Monthly Archives: May 2024

Patrik Schach and Enno Giese, physicists at TU Darmstadt, are looking to redefine timethey believe our previous measurements may have been inaccurate. The researchers have arrived at this proposal thanks to the phenomenon of quantum tunneling, where particles appear to move faster than the speed of light.

We make sense of the world around us with classical mechanics. In this realm, the laws of physics reign supreme, and particles tend to follow them. Dig a bit deeper into the quantum realm, though, and even the theory of relativity comes crashing down.

The faster-than-light travel of particles inside a quantum tunnel has prompted researchers to question whether we have accurately measured time. Schach and Giese have proposed a new experimental design to measure time for a tunneling particle, considering its unique abilities in the quantum realm.

In classical physics, a particle such as an electron can only pass through a potential energy barrier if it has the energy to overcome it. On the other hand, in quantum mechanics, the particle can cross over such a barrier even if its energy levels are lower. This is referred to as quantum tunneling.

This is attributed to the particles wave-like properties in quantum mechanics, which allow it to tunnel through the barrier even at a lower energy level. According to quantum mechanics, this tunneling is subjective to the width and height of the barrier and the particles energy.

Even though tunneling also seems to break the laws of energy conservation, the particle appears on the other side of the barrier with the same energy as before. So, no energy is gained or lost during the process.

Researchers believe that tunneling also plays a role in radioactive decay, allowing particles to escape the nucleus even though they do not have sufficient energy to escape the nuclear potential barrier. Additionally, the phenomenon could help serve applications such as microscopy and memory storage.

According to quantum mechanics, atoms can behave like waves and particles simultaneously. Their wave nature can help them overcome an energy barrier. However, when atoms are tunneling, it becomes difficult to predict when they will appear on the other side, i.e., when they need to tunnel.

Instead of relying on conventional approaches to measure time, Schach and Giese propose using the tunneling particle as a clock. A non-tunneling particle will serve as a reference in such a setup.

By comparing these two natural clocks, the researchers aim to determine whether time travels faster, slower, or equally fast when the particle is tunneling.

The researchers plan to use the oscillating energy levels between atoms to achieve this. Using a laser pulse, the researchers will oscillate the atoms and start the clock. During tunneling, a small shift in the rhythm occurs, and a second laser pulse will be used to cause the waves to interfere.

By measuring the interference, the team can precisely measure the elapsed time. The challenge, however, is that the time difference to be measured is extremely short, 10-26 seconds. To overcome this, the researchers propose using clouds of atoms instead of individual atoms to amplify the effect.

The experimental design has been published in the journal Science Advances.

NEWSLETTER

Stay up-to-date on engineering, tech, space, and science news with The Blueprint.

Ameya Paleja Ameya is a science writer based in Hyderabad, India. A Molecular Biologist at heart, he traded the micropipette to write about science during the pandemic and does not want to go back. He likes to write about genetics, microbes, technology, and public policy.

More:

Quantum tunnel: Scientists study particles that move faster than light - Interesting Engineering

It can be hard to wrap our minds round the very large and the very small. Ron Koeberer/Millennium Images, UK

Imagine setting off on a spacecraft that can travel at the speed of light. You wont get far. Even making it to the other side of the Milky Way would take 100,000 years. It is another 2.5 million years to Andromeda, our nearest galactic neighbour. And there are some 2 trillion galaxies beyond that.

The vastness of the cosmos defies comprehension. And yet, at the fundamental level, it is made of tiny particles.It is a bit of a foreign country both the small and the very big, says particle physicist Alan Barr at the University of Oxford. I dont think you ever really understand it, you just get used to it.

Still, you need to have some grasp of scale to have any chance of appreciating how reality works.

Lets start big, with the cosmic microwave background (CMB), the radiation released 380,000 years after the big bang. The biggest scales weve measured are features in the CMB, says astrophysicist Pedro Ferreira, also at the University of Oxford. These helped us put the diameter of the observable universe at 93 billion light years.

At the other end of the scale, the smallest entities are fundamental particles like quarks. Yet quantum physics paints these as dimensionless blips in a quantum field, with no size at all. So what is the shortest possible distance? The best we can do is the so-called Planck length, which is about

See the original post here:

Quantum to cosmos: Why scale is vital to our understanding of reality - New Scientist

As part of theCenter for Quantum Leaps, a signature initiative of the Arts & Sciences strategic plan, physicistKater Murchand his research group use nano-fabrication techniques toconstruct superconducting quantum circuitsthat allow them to probe fundamental questions in quantum mechanics. Qubits are promising systems for realizing quantum schemes for computation, simulation and data encryption.

Murch and his collaborators published a new paper inPhysical Review Lettersthat explores the effects of memory in quantum systems and ultimately offers a novel solution to decoherence, one of the primary problems facing quantum technologies.

Our work shows that theres a new way to prevent decoherence from corrupting quantum entanglement, said Murch, the Charles M. Hohenberg Professor of Physics at Washington University in St. Louis. We can use dissipation to prevent entanglement from leaving our qubits in the first place.

View the teams illustrated video about their research findings:https://youtu.be/EbeNagXqJEk

Learn more about WashUs quantum research in theAmpersandmagazine.

Continue reading here:

Helping qubits stay in sync - Newswise

A variation on the theory of quantum gravity the unification of quantum mechanics and Einstein's general relativity could help solve one of the biggest puzzles in cosmology, new research suggests.

For nearly a century, scientists have known that the universe is expanding. But in recent decades, physicists have found that different types of measurements of the expansion rate called the Hubble parameter produce puzzling inconsistencies.

To resolve this paradox, a new study suggests incorporating quantum effects into one prominent theory used to determine the expansion rate.

"We tried to resolve and explain the mismatch between the values of the Hubble parameter from two different prominent types of observations," study co-author P.K. Suresh, a professor of physics at the University of Hyderabad in India, told Live Science via email.

The universe's expansion was first identified by Edwin Hubble in 1929. His observations with the largest telescope of that time revealed that galaxies farther from us appear to move away at faster speeds. Although Hubble initially overestimated the expansion rate, subsequent measurements have refined our understanding, establishing the current Hubble parameter as highly reliable.

Later in the 20th century, astrophysicists introduced a novel technique to gauge the expansion rate by examining the cosmic microwave background, the pervasive "afterglow" of the Big Bang.

However, a serious problem arose with these two types of measurements. Specifically, the newer method produced a Hubble parameter value almost 10% lower than the one deduced from the astronomical observations of distant cosmic objects. Such discrepancies between different measurements, called the Hubble tension, signal potential flaws in our understanding of the universe's evolution.

Get the worlds most fascinating discoveries delivered straight to your inbox.

Related: Newfound 'glitch' in Einstein's relativity could rewrite the rules of the universe, study suggests

In a study published in the journal Classical and Quantum Gravity, Suresh and his colleague from the University of Hyderabad, B. Anupama, proposed a solution to align these disparate results. They underscored that physicists infer the Hubble parameter indirectly, employing our universe's evolutionary model based on Einstein's theory of general relativity.

The team argued for revising this theory to incorporate quantum effects. These effects, intrinsic to fundamental interactions, encompass random field fluctuations and the spontaneous creation of particles from the vacuum of space.

Despite scientists' ability to integrate quantum effects into theories of other fields, quantum gravity remains elusive, making detailed calculations extremely difficult or even impossible. To make matters worse, experimental studies of these effects require reaching temperatures or energies many orders of magnitude higher than those achievable in a lab.

Acknowledging these challenges, Suresh and Anupama focused on broad quantum-gravity effects common to many proposed theories.

"Our equation doesn't need to account for everything, but that does not prevent us from testing quantum gravity or its effects experimentally," Suresh said.

Their theoretical exploration revealed that accounting for quantum effects when describing the gravitational interactions in the earliest stage of the universe's expansion, called cosmic inflation, could indeed alter the theory's predictions regarding the properties of the microwave background at present, making the two types of Hubble parameter measurements consistent.

Of course, final conclusions can be drawn only when a full-fledged theory of quantum gravity is known, but even the preliminary findings are encouraging. Moreover, the link between the cosmic microwave background and quantum gravitational effects opens the way to experimentally studying these effects in the near future, the team said.

"Quantum gravity is supposed to play a role in the dynamics of the early universe; thus its effect can be observed through measurements of the properties of the cosmic microwave background," Suresh said.

"Some of the future missions devoted to studying this electromagnetic background are highly probable and promising to test quantum gravity. It provides a promising suggestion to resolve and validate the inflationary models of cosmology in conjunction with quantum gravity."

Additionally, the authors posit that quantum gravitational phenomena in the early universe might have shaped the properties of gravitational waves emitted during that period. Detecting these waves with future gravitational-wave observatories could further illuminate quantum gravitational characteristics.

"Gravitational waves from various astrophysical sources have only been observed so far, but gravitational waves from the early universe have not yet been detected," Suresh said. "Hopefully, our work will help in identifying the correct inflationary model and detecting the primordial gravitational waves with quantum gravity features."

Read the rest here:

A new theory of quantum gravity could explain the biggest puzzle in cosmology, study suggests - Livescience.com

Quantum tunneling allows particles to bypass energy barriers. A new method has been proposed to measure the time it takes for particles to tunnel, which could challenge previous assertions of superluminal tunneling speeds. This method involves using atoms as clocks to detect subtle time differences. Credit: SciTechDaily.com

In an amazing phenomenon of quantum physics known as tunneling, particles appear to move faster than the speed of light. However, physicists from Darmstadt believe that the time it takes for particles to tunnel has been measured incorrectly until now. They propose a new method to stop the speed of quantum particles.

In classical physics, there are strict laws that cannot be circumvented. For instance, if a rolling ball lacks sufficient energy, it will not get over a hill; instead, it will roll back down before reaching the peak. In quantum physics, this principle is not quite so strict. Here, a particle may pass a barrier, even if it does not have enough energy to go over it. It acts as if it is slipping through a tunnel, which is why the phenomenon is also known as quantum tunneling. Far from mere theoretical magic, this phenomenon has practical applications, such as in the operation of flash memory drives.

In the past, experiments in which particles tunneled faster than light drew some attention. After all, Einsteins theory of relativity prohibits faster-than-light velocities. The question is therefore whether the time required for tunneling was stopped correctly in these experiments. Physicists Patrik Schach and Enno Giese from TU Darmstadt follow a new approach to define time for a tunneling particle. They have now proposed a new method of measuring this time. In their experiment, they measure it in a way that they believe is better suited to the quantum nature of tunneling. They have published the design of their experiment in the renowned journal Science Advances.

According to quantum physics, small particles such as atoms or light particles have a dual nature.

Depending on the experiment, they behave like particles or like waves. Quantum tunneling highlights the wave nature of particles. A wave packet rolls towards the barrier, comparable to a surge of water. The height of the wave indicates the probability with which the particle would materialize at this location if its position were measured. If the wave packet hits an energy barrier, part of it is reflected. However, a small portion penetrates the barrier and there is a small probability that the particle will appear on the other side of the barrier.

Previous experiments observed that a light particle has traveled a longer distance after tunneling than one that had a free path. It would therefore have traveled faster than the light. However, the researchers had to define the location of the particle after its passage. They chose the highest point of its wave packet.

But the particle does not follow a path in the classical sense, objects Enno Giese. It is impossible to say exactly where the particle is at a particular time. This makes it difficult to make statements about the time required to get from A to B.

Schach and Giese, on the other hand, are guided by a quote from Albert Einstein: Time is what you read off a clock. They suggest using the tunneling particle itself as a clock. A second particle that does not tunnel serves as a reference. By comparing these two natural clocks, it is possible to determine whether time elapses slower, faster or equally fast during quantum tunneling.

The wave nature of particles facilitates this approach. The oscillation of waves is similar to the oscillation of a clock. Specifically, Schach and Giese propose using atoms as clocks. The energy levels of atoms oscillate at certain frequencies. After addressing an atom with a laser pulse, its levels initially oscillate synchronized the atomic clock is started. During tunneling, however, the rhythm shifts slightly. A second laser pulse causes the two internal waves of the atom to interfere. Detecting the interference makes it possible to measure how far apart the two waves of the energy levels are, which in turn is a precise measure of the elapsed time.

A second atom, which does not tunnel, serves as a reference to measure the time difference between tunneling and non-tunneling. Calculations by the two physicists suggest that the tunneling particle will show a slightly delayed time. The clock that is tunneled is slightly older than the other, says Patrik Schach. This seems to contradict experiments that attributed superluminal speed to tunneling.

In principle, the test can be carried out with todays technology, says Schach, but it is a major challenge for experimenters. This is because the time difference to be measured is only around 10-26 seconds an extremely short time. It helps to use clouds of atoms as clocks instead of individual atoms, explains the physicist. It is also possible to amplify the effect, for example by artificially increasing the clock frequencies.

We are currently discussing this idea with experimental colleagues and are in contact with our project partners, adds Giese. It is quite possible that a team will soon decide to carry out this exciting experiment.

Reference: A unified theory of tunneling times promoted by Ramsey clocks by Patrik Schach and Enno Giese, 19 April 2024,Science Advances. DOI: 10.1126/sciadv.adl6078

Go here to read the rest:

Breaking Light Speed: The Quantum Tunneling Enigma - SciTechDaily

In the fascinating realm of quantum physics, particles seem to defy the laws of classical mechanics, exhibiting mind-bending phenomena that challenge our understanding of the universe. One such phenomenon is quantum tunneling.

In quantum tunnels, particles appear to move faster than the speed of light, seemingly breaking the fundamental rules set by Einsteins theory of relativity.

However, a group of physicists from TU Darmstadt has proposed a new method to measure the time it takes for particles to tunnel, suggesting that previous experiments may have been inaccurate.

Patrik Schach and Enno Giese, physicists from TU Darmstadt, have published their groundbreaking experiment design in the prestigious journal Science Advances.

Their approach aims to redefine the concept of time for a tunneling particle, taking into account the quantum nature of the phenomenon.

Quantum tunneling is a phenomenon in quantum mechanics where a particle, such as an electron, passes through a potential energy barrier that it classically cannot surmount.

In classical physics, if a particle doesnt have enough energy to overcome a barrier, it will simply bounce back or stop.

However, in quantum mechanics, particles exhibit wave-like properties, and there is a probability that the particle can tunnel through the barrier, even if it lacks the energy to cross it classically.

Here are some key points to understand about quantum tunnels:

Particles in quantum mechanics possess both wave and particle properties. The wave nature of particles allows them to exhibit behaviors that are not possible in classical physics.

The probability of a particle tunneling through a barrier depends on factors such as the barriers width and height, and the particles energy.

Quantum tunneling does not violate the law of energy conservation. The particle does not gain or lose energy while tunneling. Instead, it appears on the other side of the barrier with the same energy it had before.

Quantum tunneling has numerous practical applications, including scanning tunneling microscopy (STM), which allows scientists to image surfaces at the atomic level, and flash memory drives that use quantum tunneling to store and access data.

Quantum tunneling also plays a role in radioactive decay, where particles escape the nucleus of an atom despite not having enough energy to overcome the nuclear potential barrier.

According to quantum physics, small particles such as atoms or light particles possess a dual nature, behaving like both particles and waves depending on the experiment.

As mentioned previously, quantum tunneling highlights the wave nature of particles, where a wave packet rolls towards an energy barrier, and a small portion of it penetrates the barrier, resulting in a probability that the particle will appear on the other side.

But the particle does not follow a path in the classical sense, objects Enno Giese. It is impossible to say exactly where the particle is at a particular time. This makes it difficult to make statements about the time required to get from A to B.

Inspired by Albert Einsteins quote, Time is what you read off a clock, Schach and Giese propose using the tunneling particle itself as a clock, with a second non-tunneling particle serving as a reference.

By comparing these two natural clocks, they aim to determine whether time elapses slower, faster, or equally fast during quantum tunneling.

The researchers suggest using atoms as clocks, taking advantage of the oscillating energy levels within them. By addressing an atom with a laser pulse, its levels initially oscillate in sync, starting the atomic clock.

During tunneling, the rhythm shifts slightly, and a second laser pulse causes the two internal waves of the atom to interfere. Detecting this interference allows for precise measurement of the elapsed time.

The clock that is tunneled is slightly older than the other, says Patrik Schach, contradicting experiments that attributed superluminal speed to tunneling.

While the proposed experiment can be carried out with todays technology, it presents a significant challenge for experimenters. The time difference to be measured is extremely short, around 10-26 seconds.

To overcome this, the researchers suggest using clouds of atoms as clocks instead of individual atoms and amplifying the effect by artificially increasing the clock frequencies.

We are currently discussing this idea with experimental colleagues and are in contact with our project partners, adds Giese. The possibility of a team deciding to carry out this exciting experiment in the near future is quite real.

In summary, Patrik Schach and Enno Gieses experiment design challenges our understanding of time and particle behavior in the quantum realm.

By proposing a new method to measure the time it takes for particles to tunnel, they are questioning previous assumptions about superluminal speeds and presenting new avenues for exploring the mysteries of quantum physics.

As they collaborate with experimental colleagues and project partners, the possibility of conducting this exciting experiment draws closer, promising to unlock the secrets of the quantum universe and pave the way for a deeper understanding of the fundamental nature of reality.

The full study was published in the journal Science Advances.

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

Read the original here:

Quantum tunnels allow particles to break the light-speed barrier - Earth.com

Im not saying its all true, says Christoph Simon, a physicist at the University of Calgary in Canada. Im just saying it is not crazy to look for it. He is talking about the possibility that life has found ways to make use of quantum effects in a host of essential phenomena, from photosynthesis and the navigational abilities of birds to consciousness.

The idea has long been seen as a bit fringe, on the assumption that such fragile effects must quickly disappear in the warm, wet environment of cells. Quantumness tends to prosper in very cold systems that are carefully isolated rather than part of a tepid soup awash with other activity.

But that is beginning to change, with tentative evidence for quantum behaviours in the machinery of cells and hints that quantum biology may not play by the conventional rules governing the subatomic world, raising new questions about the boundary between the classical and quantum realms.

You could say, well, all molecules are quantum mechanical, so everything in biology is quantum mechanical, says Greg Scholes, a chemist at Princeton University. But the idea of quantum biology only really gets interesting, he says, with the possibility that it explains emergent macroscopic behaviour that cant be predicted using classical laws.

Finding such behaviour typically means searching for evidence of archetypal quantum traits such as superposition, in which a system appears to exist in multiple states simultaneously before it loses this so-called quantum coherence and collapses into one state or another a process called decoherence.

See the rest here:

Quantum biology: New clues on how life might make use of weird physics - New Scientist

Phase-controlled projection measurement of quantum erasers for superresolution

Figure1 shows a universal scheme of the classically (coherently) excited superresolution based on phase-controlled quantum erasers. The superresolution scheme in Fig.1 originates in the Nth-order intensity correlations between phase-controlled quantum erasers, resulting in the PBW-like quantum feature11,25, as shown in Fig.2. Compared to the N=4 case11,25, the Inset of Fig.1 shows an arbitrary Nth-order superresolution scheme, where the first eight quantum erasers for N=8 are visualized with dotted blocks to explain the cascaded phase control of the quantum erasers using QWPs. For the quantum eraser, both single photon8 and cw laser light9 were experimentally demonstrated in a MachZehnder interferometer (MZI) for the polarization-basis projection onto a polarizer P. The MZI physics of coherence optics37 shows the same feature in both a single photon15 and cw light due to the limited Sorkin parameter, as discussed for the Born rule tests38. This originates in the equality between quantum and classical approaches for the first-order (N=1) intensity correlation24. Quantum mechanically, the deterministic feature of the MZI system is due to the double unitary transformation of a 50/50 nonpolarizing beam splitter (BS)1,15. The use of neutral density filters is not to generate single photons but to protect photodiodes from intensity saturation.

Schematic of a universal super-resolution based on phase-controlled quantum erasers. L: laser, ND: neutral density filter, H: half-wave plate, PBS: polarizing beam splitter, PZT: piezo-electric transducer, QWP: quarter-wave plate, P: polarizer, D: single photon (or photo-) detector, All rotation angles of Ps are at (uptheta =45^circ).

Numerical calculations of the Nth order intensity correlations in Fig.1. (upperleft) Individual first-order intensity correlation ({I}_{j}) in A, B, C, and D blocks. Blue star (circle): B3 (B4) in B, Cyan star (circle): C3 (C4) in C, Red star (circle): A3 (A4) in A, Magenta star (circle): D3 (D4) in D. (upper right) Second-order intensity correlation in each block of the Inset of Fig. 1.(lower right) Fourth-order intensity correlation between (red) A and B, and (blue) C and D. (lowerleft) Eight-order intensity product between all quantum erasers. ({I}_{K}={I}_{K1}{I}_{K2}) (K=A, B, C, D), ({I}_{AB}^{(4)}={I}_{A}^{(2)}{I}_{B}^{(2)}), ({I}_{CD}^{(4)}={I}_{C}^{(2)}{I}_{D}^{(2)}), and ({I}_{ABCD}^{(8)}={I}_{AB}^{(4)}{I}_{CD}^{(4)}). ({xi }_{A}=frac{pi }{2}), ({xi }_{C}=frac{pi }{4}), and ({xi }_{D}=frac{3pi }{4}).

The rotation angle of QWP in each block of the quantum erasers in the Inset of Fig.1 is to induce a phase gains (({xi }_{j})) to the vertical component of the corresponding light37. As experimentally demonstrated25, the QWP induces a phase delay to the vertical polarization component compared to the horizontal one37. This polarization-basis-dependent phase gain of the light directly affects the quantum eraser via polarization-basis projection measurements, resulting in a fringe shift11,25, because the role of the polarizer P is to project orthogonal polarization bases onto the common axis (widehat{{text{p}}}) (see Eqs. (2)(8))8,9,18. The random path length to the polarizer from PBS in Fig.1 does not influence the intensity correlations due to the unaffected global phase by the Born rule, where intensity (measurement) is the absolute square of the amplitude13,14. Thus, controlling the QWP of each block makes an appropriate fringe shift of the quantum erasers for the first-order intensity products.

In the proposed universal scheme with a practically infinite number of phase-controlled quantum erasers in Fig.1, a general coherence solution of the phase-controlled superresolution is coherently derived from the combinations of QWPs (see Eq.(25) and Figs. 2 and 3). Then, the general solution is compared with PBWs based on N00N states for the discussion of phase quantization of the Nth-order intensity product in Fig.4. Such phase quantization has already been separately discussed for coherence de Broglie waves (CBWs) in a coupled MZI system for the wave nature of quantum mechanics39,40. Unlike CBWs resulting from MZI superposition, the present phase quantization of superresolution is for the intensity product between phase-controlled quantum erasers. On the contrary to energy quantization of the particle nature in quantum mechanics1, the phase quantization is for the wave nature, where the particle and wave natures are mutually exclusive.

Numerical calculations for the normalized Kth-order intensity products. K represents the number of quantum erasers used for intensity product measurements.

Phase quantization of the intensity products in Fig.3. K is the order of intensity product. Dotted: K=1, Cyan: K=2, Blue: K=4, Red: K=8.

A coherence approach based on the wave nature of a photon is adopted to analyze Fig.1 differently from the quantum approach based on quantum operators1,26,27,28,29,30,31,32,33. The novel feature of the present method is to use common intensity products of cw lights via polarization-basis projection of the phase-controlled quantum erasers. Thus, there is no need for single-photon coincidence detection. Instead, the intensity product is enough for a single shot measurement, as is in nonlinear optics. Technically, the condition ({text{N}}le {text{M}}) is required, where N and M are the number of quantum erasers used for the intensity product and the photon number of the input light, respectively. Here it should be noted that both intensity product and coincidence detection are effective within the ensemble coherence time of the input light L. In that sense, a pulsed laser is more appropriate for the use of a time-bin scheme as shown for quantum key distribution41.

The amplitude of the output field of the Michelson interferometer in Fig.1 is represented using the BS matrix representation42as:

$${{varvec{E}}}_{A}=frac{i{E}_{0}}{sqrt{2}}left(widehat{H}{e}^{ivarphi }+widehat{V}right)$$

(1)

where ({E}_{0}) is the amplitude of the light just before entering the Michelson interferometer. (widehat{H}) and (widehat{V}) are unit vectors of horizontal and vertical polarization bases of the light, respectively. In Eq.(1), the original polarization bases are swapped by the 45 rotated QWPs inserted in both paths for full throughput to the ({E}_{A}) direction. Due to the orthogonal bases, Eq.(1) results in no fringe, satisfying the distinguishable photon characteristics of the particle nature in quantum mechanics: (langle {I}_{A}rangle ={I}_{0}).

By the rotated polarizers in Fig.1, whose rotation angle (uptheta) is from the horizontal axis, Eq.(1) is modified for the split quantum erasers:

$${{varvec{E}}}_{A1}=frac{i{E}_{0}}{sqrt{2}sqrt{8}}left(costheta {e}^{ivarphi }+sintheta {e}^{i{xi }_{A}}right)widehat{p}$$

(2)

$${{varvec{E}}}_{A2}=frac{-{E}_{0}}{sqrt{2}sqrt{8}}left(-costheta {e}^{ivarphi }+sintheta {e}^{i{xi }_{A}}right)widehat{p}$$

(3)

$${{varvec{E}}}_{B1}=frac{-i{E}_{0}}{sqrt{2}sqrt{8}}left(costheta {e}^{ivarphi }+sintheta right)widehat{p}$$

(4)

$${{varvec{E}}}_{B2}=frac{-i{E}_{0}}{sqrt{2}sqrt{8}}left(-costheta {e}^{ivarphi }+sintheta right)widehat{p}$$

(5)

$${{varvec{E}}}_{C1}=frac{-{E}_{0}}{sqrt{2}sqrt{8}}left(costheta {e}^{ivarphi }+sintheta {e}^{i{xi }_{C}}right)widehat{p}$$

(6)

$${{varvec{E}}}_{C2}=frac{-i{E}_{0}}{sqrt{2}sqrt{8}}left(-costheta {e}^{ivarphi }+sintheta {e}^{i{xi }_{C}}right)widehat{p}$$

(7)

$${{varvec{E}}}_{D1}=frac{-i{E}_{0}}{sqrt{2}sqrt{8}}left(costheta {e}^{ivarphi }+sintheta {e}^{i{xi }_{D}}right)widehat{p}$$

(8)

$${{varvec{E}}}_{D2}=frac{{E}_{0}}{sqrt{2}sqrt{8}}left(-costheta {e}^{ivarphi }+sintheta {e}^{i{xi }_{D}}right)widehat{p}$$

(9)

where (widehat{p}) is the axis of the polarizers, and (sqrt{8}) is due to the eight divisions (N=8) of ({{varvec{E}}}_{A}) by the lossless BSs. In Eqs. (2)(9), the projection onto the polarizer results in (widehat{H}to costheta widehat{p}) and (widehat{V}to sintheta widehat{p}). By BS, the polarization direction of (widehat{H}) is reversed, as shown in the mirror image37. By the inserted QWP in each block, the ({xi }_{j})-dependent phase gain is to the (widehat{V}) component only37. As demonstrated for the projection measurement of N interfering entangled photons23,29, the Nth-order intensity correlation is conducted by the N split ports in the Inset of Fig.1.

Thus, the corresponding mean intensities of all QWP-controlled quantum erasers in the Inset of Fig.1 are as follows for (uptheta =45^circ) of all Ps:

$$langle {I}_{A1}rangle =frac{{I}_{0}}{2N}langle 1+{{cos}}(varphi -{xi }_{A})rangle$$

(10)

$$langle {I}_{A2}rangle =frac{{I}_{0}}{2N}langle 1-{{cos}}(varphi -{xi }_{A})rangle$$

(11)

$$langle {I}_{B1}rangle =frac{{I}_{0}}{2N}langle 1+cosvarphi rangle$$

(12)

$$langle {I}_{B2}rangle =frac{{I}_{0}}{2N}langle 1-cosvarphi rangle$$

(13)

$$langle {I}_{C1}rangle =frac{{I}_{0}}{2N}leftlangle 1+{cos}(varphi -{xi }_{C})rightrangle$$

(14)

$$langle {I}_{C2}rangle =frac{{I}_{0}}{2N}leftlangle 1-{cos}(varphi -{xi }_{C})rightrangle$$

(15)

$$langle {I}_{D1}rangle =frac{{I}_{0}}{2N}leftlangle 1+{cos}(varphi -{xi }_{D})rightrangle$$

(16)

$$langle {I}_{D2}rangle =frac{{I}_{0}}{2N}leftlangle 1-{cos}(varphi -{xi }_{D})rightrangle$$

(17)

Equations(10)(17) are the unveiled quantum mystery of the cause-effect relation of the quantum eraser found in the ad-hoc polarization-basis superposition via the polarization projection onto the (widehat{p}) axis of the polarizer. The price to pay for this quantum mystery is 50% photon loss by the polarization projection11,22, regardless of single photons8 or cw light9. By adjusting ({xi }_{j}) of QWP in each block, appropriate fringe shifts of the quantum erasers can also be made accordingly, as shown in Fig.2 for ({xi }_{A}=frac{pi }{2}), ({xi }_{C}=frac{pi }{4}), and ({xi }_{D}=frac{3pi }{4}).

The corresponding second-order (N=2) intensity correlations between the quantum erasers in each block is directly obtained from Eqs. (10)(17) for ({xi }_{A}=frac{pi }{2}), ({xi }_{C}=frac{pi }{4}), and ({xi }_{D}=frac{3pi }{4}):

$$leftlangle {{text{I}}}_{A1A2}^{(2)}(0)rightrangle ={left(frac{{I}_{0}}{2N}right)}^{2}leftlangle {sin}^{2}left(varphi -frac{pi }{2}right)rightrangle$$

(18)

$$leftlangle {{text{I}}}_{B1B2}^{(2)}(0)rightrangle ={left(frac{{I}_{0}}{2N}right)}^{2}leftlangle {sin}^{2}varphi rightrangle$$

(19)

$$leftlangle {{text{I}}}_{C1C2}^{(2)}(0)rightrangle ={left(frac{{I}_{0}}{2N}right)}^{2}leftlangle {sin}^{2}left(varphi -frac{pi }{4}right)rightrangle$$

(20)

$$leftlangle {{text{I}}}_{D1D2}^{(2)}(0)rightrangle ={left(frac{{I}_{0}}{2N}right)}^{2}leftlangle {sin}^{2}left(varphi -frac{3pi }{4}right)rightrangle$$

(21)

where the second-order intensity fringes are also equally shifted as in the first-order fringes (see Fig.2). Likewise, the fourth-order (N=4) intensity correlations between any two blocks can be derived from Eqs. (18)(21) as:

$$leftlangle {{text{I}}}_{A1A2B1B2}^{(4)}(0)rightrangle ={left(frac{{I}_{0}}{2N}right)}^{4}leftlangle {sin}^{2}varphi {sin}^{2}left(varphi -frac{pi }{2}right)rightrangle$$

(22)

$$leftlangle {{text{I}}}_{C1C2D1D2}^{(4)}(0)rightrangle ={left(frac{{I}_{0}}{2N}right)}^{4}leftlangle {sin}^{2}left(varphi -frac{pi }{4}right){sin}^{2}left(varphi -frac{3pi }{4}right)rightrangle$$

(23)

Thus, the eighth-order (N=8) intensity correlation for all quantum erasers in the Inset of Fig.1 is represented as:

$$leftlangle {{text{I}}}_{A1A2B1B2C1C2D1D2}^{(8)}(0)rightrangle ={left(frac{{I}_{0}}{2N}right)}^{8}leftlangle {sin}^{2}varphi {sin}^{2}left(varphi -frac{pi }{4}right){sin}^{2}left(varphi -frac{pi }{2}right){sin}^{2}left(varphi -frac{3pi }{4}right)rightrangle$$

(24)

From Eq.(24), the proposed scheme of superresolution for N=8 is analytically confirmed for the satisfaction of the Heisenberg limit in quantum sensing (see Figs. 2 and 3).

Figure2 shows numerical calculations of the Nth-order intensity correlations using Eqs. (10)(17) for ({xi }_{A}=uppi /2), ({xi }_{C}=uppi /4), and ({xi }_{D}=3uppi /4) to demonstrate the proposed PBW-like superresolution using phase-controlled coherent light in Fig.1. From the upper-left panel to the clockwise direction in Fig.2, the simulation results are shown for ordered (N=1, 2, 4, 8) intensity correlations. As shown, all ordered-intensity correlations are equally spaced in the phase domain, where the pair of quantum erasers in each block satisfies the out-of-phase relation (see the same colored o and * curves in the upper-left panel). Thus, the higher-order intensity correlation between blocks also results in the same out-of-phase relation, as shown for N=2 and N=4, resulting in the Heisenberg limit, (mathrm{delta varphi }=uppi /{text{N}}).

For an arbitrary order N, the jth block with ({xi }_{j})-QWP can be assigned to the universal scheme of the phase-controlled superresolution. For the expandable finite block series with ({xi }_{j})-phase-controlled quantum erasers in Fig.1, the generalized solution of the kth-order intensity correlation can be quickly deduced from Eq.(24):

$$leftlangle {{text{I}}}^{(K)}(0)rightrangle ={left(frac{{I}_{0}}{2N}right)}^{K}leftlangle prod_{j=0}^{K}{sin}^{2}(varphi -{xi }_{j})rightrangle$$

(25)

where ({xi }_{j}=j2pi /N) and ({text{K}}le {text{N}}). Unlike the N00N-based superresolution in quantum sensing26,27,28,29,30,31, the kth-order intensity product in Eq.(25) can be coherently amplified as usual in classical (coherence) sensors. Thus, the reduction by ({left(frac{{I}_{0}}{2N}right)}^{k}) has no critical problem for potential applications of the proposed superresolution.

Figure3 is for the details of numerical calculations for K=1,2,...,8 and K=80 using Eq.(25). The top panels of Fig.3 are for odd and even Ks, where the fringe number linearly increases as K increases, satisfying the Heisenberg limit31. For the K-proportional fringe numbers, the positions of the first fringes for K=1,2,...,8 move from (uppi /2) for K=1 (black dot, left panel) to (uppi /16) for K=8 (blue dot, middle panel). As in PBWs, thus, the same interpretation of the K-times increased effective frequency to the original frequency of the input light can be made for the Kth-order intensity correlations. Unlike N00N state-based PBWs, the intensity-product order can be post-determined by choosing K detectors out of N quantum erasers.

The right panel of Fig.3 is for comparison purposes between K=8 and K=80, where the resulting ten times increased fringe numbers indicate ten times enhanced phase resolution, satisfying the Heisenberg limit. Thus, the pure coherence solution of the PBW-like quantum feature satisfying the Heisenberg limit is numerically confirmed for the generalized solution of Eq.(25). Here, the coincidence detection in the particle nature of quantum sensing with N00N states is equivalent to the coherence intensity-product measurement, where the coherence between quantum erasers is provided by the cw laser L within its spectral bandwidth. Furthermore, the ({xi }_{j}) relation between blocks composed of paired quantum erasers may imply the phase relation between paired entangled photons (discussed elsewhere).

Figure4 discusses the perspective of the phase-basis relation provided by ({xi }_{j}) in Eq.(25) for the Kth-order intensity correlations of the proposed superresolution. From the colored dots representing the first fringes of the ordered intensity products, the generalized phase basis of the Kth-order intensity correlation can be deduced for ({mathrm{varphi }}_{K}=uppi /{text{K}}). Thus, the Kth-order intensity correlation behaves as a K-times increased frequency ({f}_{K} (=K{f}_{0})) to the original input frequency ({f}_{0}) of L. The intensity-order dependent effective frequency ({f}_{K}) is equivalent to the PBW of the N00N state in quantum metrology26,27,28,29,30,31,32.

Based on the K-times increased fringes in the Kth-order intensity product, the numerical simulations conducted in Fig.4 can be interpreted as phase quantization of the intensity products through projection measurements of the quantum erasers. As shown in the PBW-like quantum features, these discrete eigenbases of the intensity products can also be compared to a K-coupled pendulum system43, where the phase quantization in Fig.4 can be classically understood39,40. Unlike the N-coupled pendulum system43 or CBWs from MZI interference39,40, however, any specific mode of ({varphi }_{K}) can be deterministically taken out by post-selection of a particular number of blocks used for the intensity-product order K in Fig.1. Like the energy quantization of the particle nature in quantum mechanics, thus, Fig.4 is another viewpoint of the wave nature for the proposed superresolution. By the wave-particle duality in quantum mechanics, both features of the energy and phase quantization are mutually exclusive.

From the universal scheme of the superresolution based on the phase-controlled quantum erasers in Fig.1, a generalized solution of the Kth-order intensity correlation in Fig.4 can also be intuitively obtained:

$$leftlangle {{text{I}}}_{{P}_{1}{P}_{2}dots {P}_{j}dots {P}_{K/2}}^{(K)}(0)rightrangle ={left(frac{{I}_{0}}{2N}right)}^{K}leftlangle {sin}^{2}(Kvarphi /2)rightrangle$$

(26)

where ({P}_{j}={Z}_{1}{Z}_{2}), and ({Z}_{j}) is the jth quantum eraser of the P block. Here, the effective phase term (Kvarphi) in Eq.(26) represents the typical nonclassical feature of PBWs used for quantum sensing with N00N states 30,31. The numerical simulations of Eq.(26) for N=1, 2, 4, and 8 perfectly match those in Fig.4 (not shown). Although the mathematical forms between Eqs. (25) and (26) are completely different, their quantum behaviors are the same as each other. Thus, Eq.(26) is equivalent to the superresolution in Eq.(25) 13,25, where the phase quantization is accomplished by ordered intensity products of the divided output fields of the Michelson interferometer. Unlike coincidence detection between entangled photons under the particle nature26,27,28,29,30,31,32, the present coherence scheme with the wave nature is intrinsically deterministic within the spectral bandwidth of the input laser. Thus, the coincidence detection in N00N-based quantum sensing is now replaced by the intensity product between independently phase-controlled quantum erasers using QWPs. Such a coherence technique of the individually and independently controlled quantum erasers can be applied for a time-bin scheme with a pulsed laser, where intensity products between different time bins are completely ignored due to their incoherence feature41.

Continue reading here:

Coherently excited superresolution using intensity product of phase-controlled quantum erasers via polarization-basis ... - Nature.com

CAMBRIDGE, Mass. Could moving atoms closer together than ever before open the door to the next quantum breakthrough? Physicists at the Massachusetts Institute of Technology have developed a new technique that allows them to arrange atoms in two distinct layers separated by a mere 50 nanometers about 2,000 times thinner than a human hair. This monumental achievement opens up exciting possibilities for studying exotic quantum phenomena and developing novel technologies.

The study, published in Science andled by Professor Wolfgang Ketterle, used laser light to trap and cool dysprosium atoms to ultra-low temperatures near absolute zero. At these extreme conditions, the atoms behave more like waves than particles, enabling researchers to manipulate them with exquisite precision.

Imagine a pair of invisible sheets, each made up of a single layer of atoms. Now, picture bringing those sheets so close together that theyre almost touching, but not quite. Thats essentially what the MIT scientists have accomplished, except on a scale so tiny its difficult to wrap your head around.

To put it in perspective, if an atom were the size of a marble, the two layers would be separated by just a few inches. But because atoms are so incredibly small, the actual distance between the layers is only 50 nanometers. Thats like taking two pieces of paper and holding them apart with a single strand of spider silk.

We have gone from positioning atoms from 500 nanometers to 50 nanometers apart, and there is a lot you can do with this, says Wolfgang Ketterle, the John D. MacArthur Professor of Physics at MIT, in a media release. At 50 nanometers, the behavior of atoms is so much different that were really entering a new regime here.

Creating these atomic bilayers required a clever trick. The researchers used two different colors of laser light, each one specifically tuned to interact with atoms in a particular quantum state, or energy level. Its a bit like having two TV remote controls, one for each layer of atoms. By carefully adjusting the laser beams, they were able to trap the atoms and move them around with nanometer precision.

What makes this setup truly special is the way the atoms in the two layers interact with each other. Even though theyre not physically touching, the atoms can still feel each others presence through a peculiar force called dipolar interaction. Its similar to how two tiny bar magnets would attract or repel each other, even from a short distance.

In the atomic realm, these dipolar interactions can give rise to all sorts of strange and wonderful behaviors. For example, the researchers observed that the atoms in one layer could actually talk to the atoms in the other layer and exchange energy, almost like they were engaged in a microscopic game of telephone. This phenomenon, known as sympathetic cooling, could potentially be used to build ultra-efficient refrigerators for cooling down quantum computers.

But the most exciting possibilities lie in the realm of fundamental physics. By studying how atoms behave in these closely spaced bilayers, scientists hope to gain new insights into exotic states of matter like superfluids and quantum magnets. These materials have properties that seemingly defy the laws of classical physics, such as the ability to flow without friction or resist changes in magnetic fields.

Down the road, the atomic bilayer setup could also be used as a platform for developing quantum technologies, such as ultra-precise sensors, secure communication networks, and powerful computers that can solve problems beyond the reach of any classical machine. Its a bit like having a miniature quantum playground where scientists can tinker with the building blocks of matter and see what new gadgets they can dream up.

Of course, theres still a lot of work to be done before these applications become a reality. The MIT team plans to conduct more experiments to better understand the subtle dance of dipolar interactions between the atomic layers. They also want to explore what happens when the atoms are cooled down even further to temperatures so low that quantum effects completely take over.

But even at this early stage, the results are nothing short of remarkable. By pushing the boundaries of atomic manipulation, these researchers have given us a glimpse into a world thats both strangely familiar and utterly alien a world where the rules of quantum mechanics reign supreme, and the line between science and science fiction starts to blur.

As we continue to explore this strange and wonderful frontier, one thing is clear: the future of physics is looking brighter than ever, and it all starts with a humble pair of atomic sheets, separated by a distance so small its almost hard to believe. But in the grand scheme of things, that tiny gap might just be the key to bridging the gap between the world we know and the one weve only begun to imagine.

StudyFinds Editor-in-ChiefSteve Fink contributedto this report.

Go here to see the original:

Scientists move atoms so close together it may change quantum physics forever - - Study Finds

Pan, a professor of modern physics and executive vice-president at the University of Science and Technology of China (USTC), has done pioneering work in multi-article interferometry and quantum experiments in space, the societys Fellows Directory says.

It also praises his team for having closed major loopholes for secure quantum communication associated with imperfect devices, making it a viable technology under realistic conditions.

Pan also featured on the 2017 Natures 10, the premier magazines annual list of the people who matter most in science. He had lit a fire under Chinas quantum technology efforts since returning full-time in 2008 after training in Europe, Nature said, labelling Pan as a physicist who took quantum communication to space and back.

In 2016, under Pans leadership, China launched the worlds first quantum science space satellite, Micius, with a mission to establish a secure communication line between China and Europe, a fact mentioned also in the Royal Society directory.

The Royal Society bio also lauded Pan for his achievements in quantum computing technology. His team demonstrated quantum computational advantage, validating the feasibility of quantum computing systems to outperform classical machines in solving specific problems, his bio says.

The breakthroughs made by Pans USTC team are often reported by top academic journals.

Pan is also an academician of the Chinese Academy of Sciences (CAS), Chinas premier research institute, and is director of the CAS Centre for Excellence in Quantum Information and Quantum Physics in Anhui province, where he is based with the USTC.

The USTC is not only home to leading quantum physicists such as Pan, but also an innovation hub that has spawned many start-ups, thanks to steady scientific breakthroughs, a competitive talent pool and generous local government support.

The Royal Society, formally the Royal Society of London for Improving Natural Knowledge, was founded in 1660 and is the worlds oldest continuous scientific academy.

In 2022, George Gao Fu, then head of the Chinese Centre for Disease Control and Prevention, a leading scientist in the field of virology and immunology, was elected by the society for his contribution to the fight against the Covid-19 pandemic.

Read more from the original source:

Chinas father of quantum named Royal Society fellow as US targets sector - South China Morning Post