Correlators Exceeding One in Continuous Measurements of Superconducting Qubits
Juan Atalaya, Shay Hacohen-Gourgy, Irfan Siddiqi, Alexander N. Korotkov
DOI 10.1103/PhysRevLett.122.223603 · Physical Review Letters
Active bibliographic source — not scientific approval
Bibliographic access preserves source history; it does not approve extracted materials or validate reported claims. Review warnings on each occurrence separately.
Abstract
We consider the effect of phase backaction on the correlator ⟨I(t)I(t+τ)⟩ for the output signal I(t) from continuous measurement of a qubit. We demonstrate that the interplay between informational and phase backactions in the presence of Rabi oscillations can lead to the correlator becoming larger than 1, even though |⟨I⟩|≤1. The correlators can be calculated using the generalized “collapse recipe,” which we validate using the quantum Bayesian formalism. The recipe can be further generalized to the case of multitime correlators and arbitrary number of detectors, measuring non-commuting qubit observables. The theory agrees well with experimental results for continuous measurement of a transmon qubit. The experimental correlator exceeds the bound of 1 for a sufficiently large angle between the amplified and informational quadratures, causing the phase backaction. The demonstrated effect can be used to calibrate the quadrature misalignment.
Similar papers
Geometric phases in superconducting qubits beyond the two-level approximation
similarity 0.85S. Berger et al.
Source status unknown — claims are unverified
Multi-time correlators in continuous measurement of qubit observables
similarity 0.85Juan Atalaya et al. · 2017 · arXiv:1710.05249
Source status unknown — claims are unverified
Robust, fast, and high-fidelity composite single-qubit gates for superconducting transmon qubits
similarity 0.85Hristo G. Tonchev et al.
Source status unknown — claims are unverified
Benchmarking the quality of multiplexed qubit readout beyond assignment fidelity
similarity 0.85Andras Di Giovanni et al. · 2025 · arXiv:2502.08589
Source status unknown — claims are unverified
Interaction-Free Measurements with Superconducting Qubits
similarity 0.84G. S. Paraoanu
Source status unknown — claims are unverified
Entanglement Metrology Using a Joint Readout of Superconducting Qubits
similarity 0.84J. M. Chow et al. · 2009 · arXiv:0908.1955
Source status unknown — claims are unverified