Randomization of Pulse Phases for Unambiguous and Robust Quantum Sensing

Abstract

We develop theoretically and demonstrate experimentally a universal dynamical decoupling method for robust quantum sensing with unambiguous signal identification. Our method uses randomisation of control pulses to suppress simultaneously two types of errors in the measured spectra that would otherwise lead to false signal identification. These are spurious responses due to finite-width π pulses, as well as signal distortion caused by π pulse imperfections. For the cases of nanoscale nuclear spin sensing and AC magnetometry, we benchmark the performance of the protocol with a single nitrogen vacancy centre in diamond against widely used nonrandomised pulse sequences. Our method is general and can be combined with existing multipulse quantum sensing sequences to enhance their performance.DD-based quantum sensing.-Whilst our method is applicable to any qubit sensor, we illustrate it here with single NV arXiv:1903.01559v1 [quant-ph]

Efficient and robust signal sensing by sequences of adiabatic chirped pulses

“…However, these do not compensate nonadiabatic couplings, which usually commute with the Hamiltonian during the shifts and ν might also differ from π/2. We use the pulses' relative phases to correct for such and other errors (see Appendix B), e.g., using the popular XY, KDD, or UR sequences [22][23][24][25]49,51]. These are based on composite pulses and improve population transfer and rephasing [22,49,50,52].…”

Enhancing the Robustness of Dynamical Decoupling Sequences with Correlated Random Phases

“…It is tedious to write down the expression ofÛ π (φ) in terms of the amplitude error Ω − Ω 0 and detuning error ∆. However,Û π (φ) has the general form [30,35]…”

“…Typical examples of these basic DD π pulse units are the π pulse arrangements belonging to the XY family [28], the YY8 sequence [34] and the Carr-Purcell sequence [38], which contain an even number of π pulses. To the first order of , the evolution matrix of a DD pulse unit reads [30,35]…”

“…All this has a negative impact on the reliability of general DD methods. In this respect, a recent theoretical and experimental study shows that the application of random global phases to each basic DD pulse unit of DD sequences suppresses, up to some extent, the spurious harmonic response while enhancing the sequence robustness against control errors [35].…”

Practical Applications of Quantum Sensing: A Simple Method to Enhance the Sensitivity of Nitrogen-Vacancy-Based Temperature Sensors

“…Assuming ν of the order of 1 MHz and C ≈ 0.3, a single N-V can potentially exhibit a sensitivity better than 0.76 K/Hz 1/2 [29]. This value of sensitivity can be improved to 5 mK/Hz 1/2 [22] using advanced protocols based on pulsed excitation and control [30,31], e.g. based on Rabi oscillations and Ramsey sequences [22][23][24], or frequency modulation [26,27].…”