January 28, 2023

Quantum researchers create an error-correcting qubit

Yale physicists have developed an error-correcting cat qubit—a new device that combines the Schrödinger’s cat concept of superposition (a physical system existing in two states at once) with the ability to fix some of the trickiest errors in a quantum computation.

Quantum superpositions of macroscopically distinct classical states—so-called Schrödinger cat states—are a resource for quantum metrology, quantum communication and quantum computation.

The team experimentally demonstrated a method for the generation and stabilization of Schrödinger cat states based on the interplay between Kerr nonlinearity and single-mode squeezing in a superconducting microwave resonator.

Unlike the multiple physical qubits needed to maintain one effective qubit, a single cat qubit can prevent phase flips all by itself. The cat qubit encodes an effective qubit into superpositions of two states within a single electronic circuit—in this case a superconducting microwave resonator whose oscillations correspond to the two states of the cat qubit.

They performed all single-qubit gate operations on timescales more than sixty times faster than the shortest coherence time and demonstrated single-shot readout of the protected qubit under stabilization.

The researchers said they are able to change their cat qubit from any one of its superposition states to any other superposition state, on command. In addition, the researchers developed a new way of reading out—or identifying—the information encoded into the qubit.

These results showcase the combination of fast quantum control and robustness against errors, which is intrinsic to stabilized macroscopic states, as well as the potential of of these states as resources in quantum information processing. (Phys.org)

The study appears in the journal Nature

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