Beating the Ramsey limit on sensing with deterministic qubit control

• URL: http://arxiv.org/abs/2408.15926v1
• Date: Wed, 28 Aug 2024 16:40:01 GMT
• Title: Beating the Ramsey limit on sensing with deterministic qubit control
• Authors: M. O. Hecht, Kumar Saurav, Evangelos Vlachos, Daniel A. Lidar, Eli M. Levenson-Falk,
• Abstract summary: We introduce a protocol for enhancing the sensitivity of a measurement of a qubit's frequency in the presence of decoherence. We demonstrate our protocol on a superconducting qubit, enhancing SNR per measurement shot by 1.65$times$ and SNR per qubit evolution time by 1.09$times$.
• Score: 4.596249232904721
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Quantum sensors promise revolutionary advances in medical imaging, energy production, mass detection, geodesy, foundational physics research, and a host of other fields. In many sensors, the signal takes the form of a changing qubit frequency, which is detected with an interference measurement. Unfortunately, environmental noise decoheres the qubit state, reducing signal-to-noise ratio (SNR). Here we introduce a protocol for enhancing the sensitivity of a measurement of a qubit's frequency in the presence of decoherence. We use a continuous drive to stabilize one component of the qubit's Bloch vector, enhancing the effect of a small static frequency shift. We demonstrate our protocol on a superconducting qubit, enhancing SNR per measurement shot by 1.65$\times$ and SNR per qubit evolution time by 1.09$\times$ compared to standard Ramsey interferometry. We explore the protocol theoretically and numerically, finding maximum enhancements of 1.96$\times$ and 1.18$\times$, respectively. We also show that the protocol is robust to parameter miscalibrations. Our protocol provides an unconditional enhancement in signal-to-noise ratio compared to standard Ramsey interferometry. It requires no feedback and no extra control or measurement resources, and can be immediately applied in a wide variety of quantum computing and quantum sensor technologies to enhance their sensitivities.

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