Squeezing extends a qubit’s bit-flip lifetime to 22 seconds
A peer-reviewed experiment extended one error-channel lifetime in a bosonic qubit from 138 milliseconds to 22 seconds at the same phase-error cost. Squeezing the quantum state changed its geometry without adding photons. The result concerns one error channel rather than preservation of all quantum information for 22 seconds, while phase errors and pump noise remain constraints on the laboratory device.
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A longer interval between bit flips
Squeezing a quantum state sharply increased the interval between bit flips in a laboratory qubit. The peer-reviewed experiment tested a bosonic qubit, which stores information in the states of an oscillator. A squeezed cat state resisted bit flips much longer than a standard cat state at the same phase-error level.[1], [2]
At a phase-flip lifetime of 1.3 microseconds, the bit-flip lifetime rose from 138 milliseconds to 22 seconds, a 160-fold gain. Mean photon numbers were 4.9 for the standard state and 4.1 for the squeezed state. The measured improvement concerns one error channel; preserving an arbitrary quantum state also requires control of phase errors.[1]
Geometry changes the error balance
Cat codes use two opposite coherent states of an oscillator. Their overlap falls as the states separate, suppressing bit flips, but adding photons increases phase flips. The researchers instead reshaped the uncertainty distribution by squeezing it. An additional longitudinal parametric pump supplied the control on the existing circuit, without requiring a new chip design. The team calls the deformed state a mooncat.[1]
Operations were tested too
A single-qubit Zeno Z gate operated 1.6 times faster at the same optimal phase-flip lifetime, while its phase-flip probability fell by a factor of 1.5. Additional pumps also introduced noise and increased photon loss. At very low bit-flip rates, the measurements reached an unexplained saturation. The demonstrated operation is a step within the tested component; two-qubit gate expectations and a complete fault-tolerant computer remain beyond this experiment.[1]
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