World’s largest Schrödinger’s Cat brings quantum into the wider world
Researchers in Switzerland have created the world largest ‘Schrödinger’s Cat’: a sapphire crystal weighing 16µg that is in two different quantum states simultaneously.
This could be used for ultrasensitive sensors for measuring gravity or dark matter in the universe or to boost quantum data storage systems.
The team of researchers at ETH Zurich is led by Prof Yiwen Chu at the Laboratory for Solid State Physics. They created the substantially heavier ‘cat’ by putting the crystal into a superposition of two opposing oscillation states simultaneously connected to a superconducting quantum qbit. Previous examples were only a few atoms.
The link between the qubit and the crystal ‘cat’ is not a Geiger counter and poison, but rather a layer of piezoelectric material that creates an electric field when the crystal changes shape while oscillating. That electric field can be coupled to the electric field of the qubit, and the superposition state of the qubit can be transferred to the crystal.
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“By putting the two oscillation states of the crystal in a superposition, we have effectively created a Schrödinger cat weighing 16 micrograms,” said Chu.
In order for the oscillation states to be true cat states, it is important that they be macroscopically distinguishable. This means that the separation of the states should be larger than any thermal or quantum fluctuations of the positions of the atoms inside the crystal. Chu and her colleagues checked this by measuring the spatial separation of the two states using the superconducting qubit.
In the future, Chu would like to push the mass limits of her crystal cats even further. “This is interesting because it will allow us to better understand the reason behind the disappearance of quantum effects in the macroscopic world,” she says.
The technique could also be used to make quantum information stored in qubits more robust by using cat states made up of a huge number of atoms in a crystal rather than relying on single atoms or ions.
