Related papers: Qubit Readout via State-Dependent Radiative Linewidths

Qubit Readout via State-Dependent Radiative Linewidths

URL: http://arxiv.org/abs/2606.31011v1
Date: Tue, 30 Jun 2026 00:55:51 GMT
Title: Qubit Readout via State-Dependent Radiative Linewidths
Abstract summary: We formulate a linewidth-encoded quantum non-demolition measurement channel in which the qubit state enters the external radiative amplitude.<n>We show analytically that this dissipative channel imprints state information on the output field at $O(t)$, whereas standard dispersive readout starts at $O(t2)$.
Score: 16.179486478300156
License: http://creativecommons.org/licenses/by/4.0/
Abstract: Fast qubit readout conventionally encodes state information in a dispersive frequency shift. Here we formulate a linewidth-encoded quantum non-demolition measurement channel in which the qubit state enters the external radiative amplitude, equivalently a state-dependent Lindblad jump operator. Starting from an empty cavity, we show analytically that this dissipative channel imprints state information on the output field at $O(t)$, whereas standard dispersive readout starts at $O(t^2)$ because it requires intracavity buildup and conditional phase accumulation. This short-time scaling produces faster matched-filter signal-to-noise ratio accumulation and persists in finite-resource comparisons, including photon-number limits, external-linewidth budgets, cavity depletion, and pulse-optimized dispersive baselines. We further outline an auxiliary-mode route that converts a qubit-state-dependent auxiliary susceptibility into a state-dependent linewidth. These results identify engineered dissipation as an information-carrying resource for fast quantum non-demolition readout.

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