Quantum metrology with imperfect measurements
- URL: http://arxiv.org/abs/2109.01160v2
- Date: Thu, 7 Jul 2022 04:21:44 GMT
- Title: Quantum metrology with imperfect measurements
- Authors: Yink Loong Len, Tuvia Gefen, Alex Retzker, Jan Ko{\l}ody\'nski
- Abstract summary: We show that in canonical scenarios involving $N$ probes with local measurements undergoing readout noise, the optimal sensitivity depends crucially on the control operations allowed to counterbalance the measurement imperfections.
We illustrate our findings with an example of NV-centre magnetometry, as well as schemes involving spin-$1/2$ probes with bit-flip errors affecting their two-outcome measurements.
- Score: 0.0
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: The impact of measurement imperfections on quantum metrology protocols has
not been approached in a systematic manner so far. In this work, we tackle this
issue by generalising firstly the notion of quantum Fisher information to
account for noisy detection, and propose tractable methods allowing for its
approximate evaluation. We then show that in canonical scenarios involving $N$
probes with local measurements undergoing readout noise, the optimal
sensitivity depends crucially on the control operations allowed to
counterbalance the measurement imperfections -- with global control operations,
the ideal sensitivity (e.g.~the Heisenberg scaling) can always be recovered in
the asymptotic $N$ limit, while with local control operations the
quantum-enhancement of sensitivity is constrained to a constant factor. We
illustrate our findings with an example of NV-centre magnetometry, as well as
schemes involving spin-$1/2$ probes with bit-flip errors affecting their
two-outcome measurements, for which we find the input states and control
unitary operations sufficient to attain the ultimate asymptotic precision.
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