Nitrogen Vacancy (NV) centers in diamond have emerged over the past few years as well-controlled quantum systems, with promising applications ranging from quantum information science to magnetic sensing. In this talk, I will first briefly introduce the NV center system, as well as the experimental methods used for measuring them and controlling their quantum spin dynamics. I will then describe two recent experiments utilizing the magnetic sensing capabilities of NVs.
Specifically, we measure the magnetization reorientation induced by chiral molecules adsorbed on the surface of a sample with a thin Cobalt layer, suggesting a persistent effect originating from strong exchange interactions. In addition, we image the spatial structure of magnetization in thin van-der-Waals magnets across the phase transition, providing insights into the dynamics of the magnetic domains across the transition.
The study of open quantum systems, quantum thermodynamics and quantum many-body spin physics in realistic solid-state platforms, has been a long-standing goal in quantum and condensed-matter physics. In this talk I will address these topics through the platform of nitrogen-vacancy (NV) spins in diamond, in the context of purification (or cooling) of a spin bath as a quantum resource and for enhanced metrology. I will first describe a general theoretical framework we developed for Hamiltonian engineering in an interacting spin system . I will then extend this framework to coupling of the spin ensemble to a spin bath, including both coherent and dissipative dynamics . Using these tools I will present a scheme for efficient purification of the spin bath, surpassing the current state-of-the-art and providing a path toward applications in quantum technologies, such as enhanced MRI sensing.
The study of many-body quantum systems, and specifically spin systems, is a main pillar of quantum physics. As part of this research direction, various experimental platforms have emerged which allow for controlled experiments in this context, with nitrogen vacancy (NV) ensembles in diamond being one of them. In order to realize relevant experiments in the NV system, advanced controlled schemes are required in order to generate the required interacting spin Hamiltonians, as well as to robustly control such dense spin ensembles. Here we tackle both issues: we develop a framework for Hamiltonian engineering based on the icosahedral symmetry group, demonstrating its advantages over existing schemes in terms of obtainable interacting Hamiltonians; we develop and demonstrate robust control pulses based on rapid adiabatic passage (RAP), which result in improved coherence times and sensing.
The study of quantum many-body spin physics in realistic solid-state platforms has been a long-standing goal in quantum and condensed-matter physics. We demonstrate separate steps required to reach this goal using nitrogen-vacancy (NV) centers in diamond. First, standard (TEM) electron irradiation is used for the enhancement of N to NV conversion efficiencies by over an order-of-magnitude. Second, robust pulsed and continuous dynamical decoupling (DD) techniques enable the preservation of arbitrary states of the ensemble. These combined efforts could lead to the desired interaction-dominated regime. Finally, we simulate the effects of continuous and pulsed microwave (MW) control on the resulting NV-NV many body dynamics in a realistic spin-bath environment. We emphasize that dominant interaction sources could be identified and decoupled by the application of proper pulse sequences, and the modification of such sequences could lead to the creation engineered interaction Hamiltonians. Such interaction Hamiltonians could pave the way toward the creation of non-classical states, e.g. spin-squeezed states, which were not yet demonstrated in the solid-state, and could eventually lead to magnetic sensing beyond the standard quantum limit (SQL).
KEYWORDS: Signal to noise ratio, Plasmonics, Diamond, Polarization, Magnetism, Sensing systems, Antennas, Magnetic sensors, Quantum physics, Neodymium, Color centers, Stereolithography, Quantum information
Nitrogen-Vacancy (NV) color centers in diamond have emerged as promising quantum solid-state systems, with applications ranging from quantum information processing to magnetic sensing. One of the most useful properties of NVs is the ability to read their ground-state spin projection optically at room temperature. In this work we consider the eﬀect of the Purcell enhancement on the ability to initialize the NV state and analyze the eﬀect to imperfect initialization on the measurement SNR. We demonstrate that even with feasible initial conditions the combined increase in spontaneous emission (through Purcell enhancement) and in optical excitation could signiﬁcantly increase the readout SNR.
In this work, we optimize a dynamical decoupling (DD) protocol to improve the spin coherence properties of a dense ensemble of nitrogen-vacancy (NV) centers in diamond. Using liquid nitrogen-based cooling and DD microwave pulses, we increase the transverse coherence time T2 from ∼ 0.7 ms up to ∼ 30 ms. We extend previous work of single-axis (Carr-Purcell-Meiboom-Gill) DD towards the preservation of arbitrary spin states. After performing a detailed analysis of pulse and detuning errors, we compare the performance of various DD protocols. We identify that the concatenated XY8 pulse sequences serves as the optimal control scheme for preserving an arbitrary spin state. Finally, we use the concatenated sequences to demonstrate an immediate improvement of the AC magnetic sensitivity up to a factor of two at 250 kHz. For future work, similar protocols may be used to increase coherence times up to NV-NV interaction time scales, a major step toward the creation of quantum collective NV spin states.