We have achieved the following results:
1) The field of quantum sensing explores the use of quantum phenomena to measure a broad range of physical quantities, of both static and time-dependent types. While for static signals the main figure of merit is sensitivity, for time dependent signals it is spectral resolution, i.e. the ability to resolve two different frequencies. We have studied the resolution problem, and developed new superresolution methods that rely on quantum features. We have formulated a general criterion for superresolution in quantum problems. Inspired by this, we have shown that quantum detectors can resolve two frequencies from incoherent segments of the signal, irrespective of their separation, in contrast to what is known about classical detection schemes.
2) We developed a novel scheme for mixed dynamical decoupling, where we combined continuous dynamical decoupling with robust sequences of phased pulses. Specifically, we used two fields for decoupling, where the first continuous driving field creates dressed states that are robust to environmental noise. Then, a second field implements a robust sequence of phased pulses to perform inversions of the dressed qubits, thus achieving robustness to amplitude fluctuations of both fields. We have shown that the proposed scheme outperforms standard concatenated continuous dynamical decoupling in realistic numerical simulations for dynamical decoupling in NV centers in diamond. Finally, we also demonstrated how our technique can be utilized for improved sensing.
3) We have developed a novel concept of velocimetry at the nano-scale which is based on quantum sensing. We have shown that quantum sensing can outperform classical methods for measuring velocities at the nano-sclae. Our scheme can be applied for the investigation of microfluidic channels, where the drift velocity is usually low and the flow properties are currently unclear. A better understanding of these properties is essential for the future development of microfluidic and nanofluidic infrastructures.
4) We have introduced the concept of deep learning enhancement of nano - NMR. We have shown that deep learning is a crucial ingredient to quantum sensing in general.
Moreover, the deep learning discrimination scheme outperform Bayesian methods when verified on noisy experimental data obtained by a single Nitrogen-Vacancy center. In the case of frequency resolution we have shown that this approach outperforms Bayesian methods even when the latter have full pre-knowledge of the noise model and the former has none. These deep learning algorithms also emerge as much more efficient in terms of computational resources and run times. Since in many real-world scenarios the noise is complex and difficult to model, we argue that deep learning is likely to become a dominant tool in the field.
5) Improvement of the Qdyne method in terms of resolution and robustness. A) The robustness work was published in(Chu et. al., Phys. Rev. Applied 15, 014031 – (2021)) as well as (Salhov et. al., in preparation). B) We have analyzed the interplay of the Qdyne method and dynamical decoupling in terms of resolution (Oviedo et. al., in preparation) and have shown that the cusp method proves superior when combined with Qdyne.
6) I have analyzed quantum sensing in the limited detection limit. (Schmitt et. al. npj Quantum Inf 7, 55 (2021) and Gefen et. al., in preparation).)
7) We have worked extensively on the resolution enhanced cusp effect. A few papers are to be published (one sent to nano letters).
8) We have extensively worked on the problem of quantum sensing enhanced by error correction. As we have understood that the current gates are not equipped for that, we have designed a series of novel gates. (Rotem et. al., in preparation).
Specifically in the final period we have presentes a novel "balanced-control" protocol for dressed qubits that eliminates the detrimental counter-rotating term using only a single lab-frame coupling axis, thereby removing the limitations imposed by the dressed rotating-wave approximation. By generating a circularly polarized field in the rotating frame, the method avoids the dynamic complications and inefficiencies of standard linear driving schemes. We have demonstrated significant performance enhancements across several quantum technologies, including a ~27-fold reduction in two-qubit gate infidelity (achieving rates below the fault-tolerant threshold) , a 10-fold increase in sensitivity for high-frequency quantum sensing , and a 5-fold extension of coherence times in atomic clock applications. Additionally, we derived a practical coherence time formula based on Floquet theory to facilitate experimental optimization and design.
