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Heralded state preparation in a superconducting qubit
J. E. Johnson, C. Macklin, D. H. Slichter, R. Vijay, E. B. Weingarten, John Clarke, I. Siddiqi
TL;DR
Achieving fast, high-fidelity quantum nondemolition readout of superconducting qubits has been difficult, with prior schemes limited by visibility, measurement time, or state demolition. A fast readout measurement heralds ground-state initialization before qubit manipulation, with non-ground-state records discarded. Ground-state heralding improved readout fidelity by 2.9 ± 0.2%.
Problem
Achieving fast, high-fidelity quantum nondemolition readout of superconducting qubits has been difficult, with prior schemes limited by visibility, measurement time, or state demolition.
Source: p. 1Method
A fast readout measurement heralds ground-state initialization before qubit manipulation, with non-ground-state records discarded.
Source: pp. 1, 3Results
Ground-state heralding improved readout fidelity by 2.9 ± 0.2%.
Source: p. 3Takeaways & Limitations
Heralding may enable rapid qubit reset without changing detuning to induce Purcell relaxation.
Source: p. 4
Abstract
from arXiv · showhide
We demonstrate high-fidelity, quantum nondemolition, single-shot readout of a superconducting flux qubit in which the pointer state distributions can be resolved to below one part in 1000. In the weak excitation regime, continuous measurement permits the use of heralding to ensure initialization to a fiducial state, such as the ground state. This procedure boosts readout fidelity to 93.9% by suppressing errors due to spurious thermal population. Furthermore, heralding potentially enables a simple, fast qubit reset protocol without changing the system parameters to induce Purcell relaxation.