Multiplexed photon number measurement

Abstract

When a two-level system -- a qubit -- is used as a probe of a larger system, it naturally leads to answering a single yes-no question about the system state. Here we propose a method where a single qubit is able to extract, not a single, but many bits of information about the photon number of a microwave resonator using continuous measurement. We realize a proof-of-principle experiment by recording the fluorescence emitted by a superconducting qubit reflecting a frequency comb, thus implementing multiplexed photon counting where the information about each Fock state -- from 0 to 8 -- is simultaneously encoded in independent measurement channels. Direct Wigner tomography of the quantum state of the resonator evidences the back-action of the measurement as well as the optimal information extraction parameters. Our experiment unleashes the full potential of quantum meters by replacing a sequential quantum measurements with simultaneous and continuous measurements separated in the frequency domain.

arXiv commentThis new version of the manuscript adds several results compared to the first versions

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Cited by in corpus (7)

• Deep Reinforcement Learning for Quantum State Preparation with Weak Nonlinear Measurements
• Single-shot number-resolved detection of microwave photons with error mitigation
• Complete physical characterization of QND measurements via tomography
• Spectroscopic estimation of the photon number for superconducting Kerr parametric oscillators
• No-Collapse Accurate Quantum Feedback Control via Conditional State Tomography
• Energetic cost of measurements using quantum, coherent, and thermal light
• Einselection from incompatible decoherence channels