Reviving the precision of multiple entangled probes in an open system by simple π -pulse sequences

Abstract

Quantum metrology with entangled states in realistic noisy environments always suffers from decoherence. Therefore, the measurement precision is greatly reduced. Here we applied the dynamical decoupling method to protect the N -qubit quantum metrology protocol and successfully revived the scaling of the measurement precision as N −k with k ∈ [5/6, 11/12]. The degree of the precision revival, as determined by the noise spectrum distribution, indicates that the performance of the protected protocol can be further improved by controlling the noise spectrum. Such a protected protocol is proved to be universal for entanglement-based quantum metrology in the pure dephasing and relaxation noise, which should stimulate the development of practical quantum metrology for weak signal detection of microscopic physics.

Non-Markovianity-assisted high-fidelity Deutsch–Jozsa algorithm in diamond

“…39,40,42 However, a recent study revealed that the memory effects of a non-Markovian environment can be regarded as important physical resources 28,33 to improve QIP in an open quantum system. To further enhance the POS of the RDJA, we utilized the memory effects of the non-Markovian environment, which can be extracted by the DD method 26,39 to mitigate imperfect operations and decoherence.…”

“…28 However, because of strong system-environment couplings, structured or finite reservoirs, low temperatures, or large initial system-environment correlations, the dynamics of an open quantum system may deviate substantially from the Born-Markov approximation and follow a non-Markovian process. [28][29][30][31][32] In such a process, the pronounced memory effect, which is the primary feature of a non-Markovian environment, can be used to revive the genuine quantum properties, [28][29][30][31][32][33][34] such as quantum coherence and correlations. Consequently, improving the performance of QIP by utilizing memory effects as important physical resources in the nonMarkovian environment is crucial.…”

Composite-pulse enhanced room-temperature diamond magnetometry

“…The hyperfine interaction with dark spin results in a random local magnetic field δ σ = ∑ A i z i i with a typical linewidth Γ 2 2 * ≈ MHz for NV ensemble as shown in µs) was measured by spin-echo sequence, as shown in Figure 2(d). Because the typical coherent control is much faster than dynamical fluctuations, we take δ as a random time independent variable [5,32]. Furthermore, we assume that NV ensemble dephasing mechanisms are independent and inhomogeneous broadening effect can be described by a Gaussian linetype P (δ) [32].…”

“…Solid-state electronic spin defects, including nitrogen vacancy (NV) [1], silicon-vacancy [2] and germaniumvacancy [3] centers in diamond, have garnered increasing relevance for quantum science and modern physics metrology. Especially, NV centers have been systematically studied and employed in interdisciplinary applications facilitated by long electron spin coherence time [4][5][6] at room-temperature. Although, a single NV center can be used for high-spatial-resolution field imaging [7,8], enhancing sensitivity are feasibly achieved by using an ensemble of N NV centers, where the shotnoise limited magnetic field sensitivity can be improved by a factor N [5,9,10].…”

“…Especially, NV centers have been systematically studied and employed in interdisciplinary applications facilitated by long electron spin coherence time [4][5][6] at room-temperature. Although, a single NV center can be used for high-spatial-resolution field imaging [7,8], enhancing sensitivity are feasibly achieved by using an ensemble of N NV centers, where the shotnoise limited magnetic field sensitivity can be improved by a factor N [5,9,10]. There have been many applications utilizing dense NV center ensembles for high-sensitivity magnetic-field sensing [9] and widefield magnetic imaging [11], such as measurements of single-neuron action potential [12], current flow in graphene [13] and chemical shift spectra from small molecules [14].…”