Physicists Create the Fattest Schrdinger’s Cat Ever – Gizmodo

Picture a cat. Im assuming youre imagining a live one. It doesnt matter. Youre wrong either waybut youre also right.

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This is the premise of Erwin Schrdingers 1935 thought experiment to describe quantum states, and now, researchers have managed to create a fat (which is to say, massive) Schrdinger cat, testing the limits of the quantum world and where it gives way to classical physics.

Schrdingers experiment is thus: A cat is in a box with a poison that is released from its container if an atom of a radioactive substance, also in the box, decays. Because it is impossible to know whether or not the substance will decay in a given timeframe, the cat is both alive and dead until the box is opened and some objective truth is determined. (You can read more about the thought experiment here.)

In the same way, particles in quantum states (qubits, if theyre being used as bits in a quantum computer) are in a quantum superposition (which is to say, both alive and dead) until theyre measured, at which point the superposition breaks down. Unlike ordinary computer bits that hold a value of either 0 or 1, qubits can be both 0 and 1 simultaneously.

Now, researchers made a Schrdingers cat thats much heavier than those previously created, testing the muddy waters where the world of quantum mechanics gives way to the classical physics of the familiar macroscopic world. Their research is published this week in the journal Science.

In the place of the hypothetical cat was a small crystal, put in a superposition of two oscillation states. The oscillation states (up or down) are equivalent to alive or dead in Schrdingers thought experiment. A superconducting circuit, effectively a qubit, was used to represent the atom. The team coupled electric-field creating material to the circuit, allowing its superposition to transfer over to the crystal. Capiche?

By putting the two oscillation states of the crystal in a superposition, we have effectively created a Schrdinger cat weighing 16 micrograms, said Yiwen Chu, a physicist at ETH Zurich and the studys lead author, in a university release.

16 micrograms is roughly equivalent to the mass of a grain of sand, and thats a very fat cat on a quantum level. Its several billion times heavier than an atom or molecule, making it the fattest quantum cat to date, according to the release.

Its not the first time physicists have tested whether quantum behaviors can be observed in classical objects. Last year, a different team declared they had quantum-entangled a tardigrade, though a number of physicists told Gizmodo that claim was poppycock.

This is slightly different, as the recent team was just testing the mass of an object in a quantum state, not the possibility of entangling a living thing. While thats not in the teams plans, working with even larger masses will allow us to better understand the reason behind the disappearance of quantum effects in the macroscopic world of real cats, Chu said.

As for the true boundary between the two worlds? No one knows, wrote Matteo Fadel, a physicist at ETH Zurich and a co-author of the paper, in an email to Gizmodo. Thats the interesting thing, and the reason why demonstrating quantum effects in systems of increasing mass is so groundbreaking.

The new research takes Schrdingers famous thought experiment and gives it some practical applications. Controlling quantum materials in superposition could be useful in a number of fields that require very precise measurements; for example, helping reduce noise in the interferometers that measure gravitational waves.

Fadel is currently studying whether gravity plays a role in the decoherence of quantum states, namely if it is responsible for the quantum-to-classical transition as proposed a couple of decades ago by Penrose. Gravity doesnt seem to exist on the subatomic level and is not accounted for in the Standard Model of particle physics.

The quantum world ripe for new discoveries, but alas, its crammed full of unknowables, dead ends, and vexing new problems.

More: Scientists Save Schrdingers Cat

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Physicists Create the Fattest Schrdinger's Cat Ever - Gizmodo