• Physics 16, 1
Research of how a nitrogen-vacancy heart’s spin interacts with a surrounding 2D layer of spins might result in new platforms for quantum metrology and simulation.
Diamond defects, nitrogen-vacancy (NV) facilities particularly, function a wealthy playground for research of spin physics. Over the previous twenty years, methods for manipulating and studying out the quantum states of NVs with optical and microwave radiation have been fine-tuned for functions of those defects as magnetometers and qubits. An necessary analysis route includes understanding and controlling how interactions with the surroundings can have an effect on the NV’s quantum properties. Now two impartial groups, led by Nathalie de Leon at Princeton College  and by Norman Yao on the College of California, Berkeley , respectively, have addressed this query for a configuration related to a number of functions: an NV heart interacting with a 2D ensemble of spins shaped by unpaired floor electrons or by impurities engineered throughout the diamond. The outcomes allowed the groups to develop improved fashions for describing how these interactions have an effect on the quantum coherence of the NV spin—data that might have profound implications for using crystal defects in each quantum metrology and quantum simulation.
Diamond has plenty of fascinating defect species, with the NV heart enjoying a starring position in optical quantum data functions . An NV is shaped by two lacking neighboring carbon atoms within the lattice, one in all which is changed by a nitrogen atom. This configuration acts as a two-level spin system that may conveniently be ready and skim out by way of lasers. A further management instrument is obtainable by means of rigorously designed microwave pulse sequences that manipulate the populations of these two ranges. Such microwave schemes can put together the NV in spin-state configurations which can be optimum for sure duties—corresponding to probing the magnetic interactions of the NV with its surroundings .
Along with such instruments, each groups exploited diamond-growth methods constantly refined since diamond NV facilities entered the quantum data scene 20 years in the past. Such methods have been instrumental in turning NVs into a few of the world’s most delicate magnetometers . The methods utilized by de Leon’s and Yao’s groups embrace rising diamond with out spinful isotopes of carbon—helpful to keep away from a lower within the NV coherence time as a consequence of interplay of the NV spin with undesired nuclear spins. One other method utilized by each teams includes enriching diamond layers with nitrogen atoms, which permits higher management on NV-center formation.
The beautiful sensitivity of NV facilities, nevertheless, generally is a double-edged sword. The power to detect nanotesla magnetic fields implies that the NV can be delicate to undesirable fields from adjoining surfaces and from different defect species current throughout the diamond crystal . These interactions result in decoherence—a loss within the quantum data saved within the NV’s electron spin states. The 2 groups of researchers take necessary steps in understanding the mechanisms by which interactions with the surroundings trigger the NV’s decoherence.
De Leon’s collaboration checked out a very insidious drawback associated to unpaired electrons on the floor of the diamond crystal. The presence of those defects has lengthy been established, however their results are nonetheless poorly understood, partly as a result of the defects are optically inactive and thus troublesome to probe instantly. The researchers used a microwave management method known as double electron–electron resonance (DEER) to review how the unpaired electrons have an effect on the decoherence of the sign collected from a single NV. Via time-resolved measurements, they obtained two notable outcomes. First, they use the acquired information to derive a mannequin that precisely describes how the decoherence time relies on the depth of the NV heart relative to the floor layer. This data might be helpful in designing NV scanning-probe sensors, whose efficiency will rely on a trade-off between sign amplitude and decoherence: small depths enhance the proximity to the probed pattern and thus the sign amplitude but additionally velocity up the decoherence and thus cut back the time over which the sign could be measured. Second, de Leon and her colleagues present that, counter to the assumptions of prevailing fashions, the floor unpaired electrons are cellular. The authors counsel that, with correct materials engineering, these defects may very well be stabilized and managed such that they may very well be utilized in superior sensors—the place the unpaired electrons act as “secondary probes” that “report” to the principle NV heart, thereby boosting its sensitivity.
Utilizing related strategies that mix DEER and microwave methods, Yao’s collaboration as an alternative explored the interplay of an NV heart with an engineered 2D layer of nitrogen impurities, often known as P1 facilities. This theoretical and experimental research lays the muse for quantum simulation and sensing platforms primarily based on a mix of NV and P1 facilities. Particularly, the researchers examine two platforms wherein various kinds of interactions dominate the scene. The primary requires the mutual interactions between NV facilities to dwarf these between NV facilities and every other defects or decoherence sources. The researchers present that they’ll entry this regime when the P1 facilities are sparse. With two totally different microwave-pulse sequences, they might put together the NV facilities in order to selectively flip off the NV facilities coupling to P1 facilities and to different NV facilities. The outcomes present that decoupling an NV from the P1 facilities solely halved the decoherence, whereas decoupling it additionally from different NVs led to a further sixfold discount in decoherence. This distinction clearly demonstrated that, on this regime, the NV–NV dipolar interplay dominates the NV–P1 interplay. The second platform, primarily based on dense P1 facilities, may very well be significantly fascinating for quantum simulation approaches involving a number of species of spins, a few of which will not be optically accessible. The workforce confirmed that it was certainly potential to switch qubit states from the intense and due to this fact simply controllable NV facilities to the optically darkish P1 facilities, proving the feasibility of those approaches.
The 2 research make strides related to quite a lot of analysis instructions. First, the sheer variety of spin defects that may be generated in platforms corresponding to these utilized by de Leon’s and Yao’s groups makes them a lot simpler to scale-up than platforms primarily based on trapped ions and impartial atoms—providing better potential for performing advanced condensed-matter quantum simulations. Second, related approaches will enable researchers to discover totally different regimes of spin physics by controlling the extent of interplay (as an example, by way of the NV depth or density) and the kind of interplay (through the use of totally different species, corresponding to NV and P1 facilities). The strategy may very well be expanded to different materials platforms, for instance silicon carbide, which, along with P1-like (spin-1/2) and NV-like (spin-1) defects, additionally hosts spin-3/2 species that might reproduce extra advanced phenomenology. Lastly, concepts for enhancing the NV sensing-resolution by way of a 2D layer of spins—just like the unpaired-electron layer studied by de Leon’s workforce—could result in ultrasensitive instruments for probing the magnetic properties of unique supplies and organic matter.
Correction (4 January 2023): The textual content was corrected to precisely describe Yao et al.’s decoupling schemes primarily based on microwave pulses. A earlier model incorrectly acknowledged that one such scheme decoupled NV facilities from different NV facilities solely, however the precise decoupling was from each NV and P1 facilities.
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Concerning the Authors
Probing Spin Dynamics on Diamond Surfaces Utilizing a Single Quantum Sensor
Bo L. Dwyer, Lila V.H. Rodgers, Elana Okay. Urbach, Dolev Bluvstein, Sorawis Sangtawesin, Hengyun Zhou, Yahia Nassab, Mattias Fitzpatrick, Zhiyang Yuan, Kristiaan De Greve, Eric L. Peterson, Helena Knowles, Tamara Sumarac, Jyh-Pin Chou, Adam Gali, V.V. Dobrovitski, Mikhail D. Lukin, and Nathalie P. de Leon
Printed December 14, 2022