Guoqing Wang

Massachusetts Institute of Technology

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Paola Cappellaro

Massachusetts Institute of Technology

Changhao Li

Xidian University

Ju Li

Massachusetts Institute of Technology

Hao Tang

Peking University

Haowei Xu

Massachusetts Institute of Technology

Danielle Braje

MIT Lincoln Laboratory

Ariel Barr

Massachusetts Institute of Technology

Yi-Xiang Liu

Southern University of Science and Technology

Jennifer M. Schloss

MIT Lincoln Laboratory

Boning Li

Massachusetts Institute of Technology

Cooperative Institutions

Massachusetts Institute of Technology

Chinese Academy of Sciences

MIT Lincoln Laboratory

University of California, Berkeley

Peking University

Lawrence Berkeley National Laboratory

Shenzhen University

Institute of Physics

University of Chinese Academy of Sciences

JPMorgan Chase & Co (United States)

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Protonation induced high- T c phases in iron-based superconductors evidenced by NMR and magnetization measurements

Science Bulletin (2017)

Yi Cui Gehui Zhang Hao‐Bo Li Hai Lin Xiyu Zhu

Mott insulator

10.1016/j.scib.2017.12.009

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Citations (54)

An integrated approach for spatio-temporal assessment and attribution of water resources carrying capacity: Incorporating AHP, TOPSIS, and lorenz asymmetry coefficient methods

Journal of Hydrology (2024)

Ting Zhou Lin Teng Ruojie Cheng Guoqing Wang Bo Jiang

TOPSIS

10.1016/j.jhydrol.2024.132536

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Fast Wide‐Field Quantum Sensor Based on Solid‐State Spins Integrated with a SPAD Array

Advanced Quantum Technologies (2023)

Guoqing Wang Francesca Madonini Boning Li Changhao Li Jinggang Xiang

Abstract Achieving fast, sensitive, and parallel measurement of a large number of quantum particles is an essential task in building large‐scale quantum platforms for different quantum information processing applications such as sensing, computation, simulation, and communication. Current quantum platforms in experimental atomic and optical physics based on CMOS sensors and charged coupled device cameras are limited by either low sensitivity or slow operational speed. Here an array of single‐photon avalanche diodes is integrated with solid‐state spin defects in diamond to build a fast wide‐field quantum sensor, achieving a frame rate up to 100 kHz. The design of the experimental setup to perform spatially resolved imaging of quantum systems is presented. A few exemplary applications, including sensing DC and AC magnetic fields, temperature, strain, local spin density, and charge dynamics, are experimentally demonstrated using a nitrogen‐vacancy ensemble diamond sample. The developed photon detection array is broadly applicable to other platforms such as atom arrays trapped in optical tweezers, optical lattices, donors in silicon, and rare earth ions in solids.

Quantum sensor

Quantum imaging

Quantum Metrology

10.1002/qute.202300046

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Citations (32)

Sensing of Arbitrary-Frequency Fields Using a Quantum Mixer

Physical Review X (2022)

Guoqing Wang Yi-Xiang Liu Jennifer M. Schloss Scott T. Alsid Danielle Braje

Quantum sensors such as spin defects in diamond have achieved excellent performance by combining high sensitivity with spatial resolution. Unfortunately, these sensors can only detect signal fields with frequency in a few accessible ranges, typically low frequencies up to the experimentally achievable control field amplitudes and a narrow window around the sensors' resonance frequency. Here, we develop and demonstrate a technique for sensing arbitrary-frequency signals by using the sensor qubit as a quantum frequency mixer, enabling a variety of sensing applications. The technique leverages nonlinear effects in periodically driven (Floquet) quantum systems to achieve quantum frequency mixing of the signal and an applied bias ac field. The frequency-mixed field can be detected using well-developed sensing techniques such as Rabi and CPMG with the only additional requirement of the bias field. We further show that the frequency mixing can distinguish vectorial components of an oscillating signal field, thus enabling arbitrary-frequency vector magnetometry. We experimentally demonstrate this protocol with nitrogen-vacancy centers in diamond to sense a 150-MHz signal field, proving the versatility of the quantum mixer sensing technique.2 MoreReceived 28 December 2021Revised 8 April 2022Accepted 5 May 2022DOI:https://doi.org/10.1103/PhysRevX.12.021061Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum controlQuantum information architectures & platformsQuantum metrologyQuantum sensingPhysical SystemsFloquet systemsQuantum InformationAtomic, Molecular & OpticalGeneral Physics

Quantum sensor

SIGNAL (programming language)

Nitrogen-vacancy center

10.1103/physrevx.12.021061

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Coherence protection and decay mechanism in qubit ensembles under concatenated continuous driving

New Journal of Physics (2020)

Guoqing Wang Yi-Xiang Liu Paola Cappellaro

Abstract Dense ensembles of spin qubits are valuable for quantum applications, even though their coherence protection remains challenging. Continuous dynamical decoupling can protect ensemble qubits from noise while allowing gate operations, but it is hindered by the additional noise introduced by the driving. Concatenated continuous driving (CCD) techniques can, in principle, mitigate this problem. Here we provide deeper insights into the dynamics under CCD, based on Floquet theory, that lead to optimized state protection by adjusting driving parameters in the CCD scheme to induce mode evolution control. We experimentally demonstrate the improved control by simultaneously addressing a dense nitrogen-vacancy (NV) ensemble with 10 10 spins. We achieve an experimental 15-fold improvement in coherence time for an arbitrary, unknown state, and a 500-fold improvement for an arbitrary, known state, corresponding to driving the sidebands and the center band of the resulting Mollow triplet, respectively. We can achieve such coherence time gains by optimizing the driving parameters to take into account the noise affecting our system. By extending the generalized Bloch equation approach to the CCD scenario, we identify the noise sources that dominate the decay mechanisms in NV ensembles, confirm our model by experimental results, and identify the driving strengths yielding optimal coherence. Our results can be directly used to optimize qubit coherence protection under continuous driving and bath driving, and enable applications in robust pulse design and quantum sensing.

Dynamical decoupling

Coherence time

10.1088/1367-2630/abd2e5

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Citations (23)

Blind quantum machine learning with quantum bipartite correlator

arXiv (Cornell University) (2023)

Changhao Li Boning Li Omar Amer Ruslan Shaydulin Shouvanik Chakrabarti

Distributed quantum computing is a promising computational paradigm for performing computations that are beyond the reach of individual quantum devices. Privacy in distributed quantum computing is critical for maintaining confidentiality and protecting the data in the presence of untrusted computing nodes. In this work, we introduce novel blind quantum machine learning protocols based on the quantum bipartite correlator algorithm. Our protocols have reduced communication overhead while preserving the privacy of data from untrusted parties. We introduce robust algorithm-specific privacy-preserving mechanisms with low computational overhead that do not require complex cryptographic techniques. We then validate the effectiveness of the proposed protocols through complexity and privacy analysis. Our findings pave the way for advancements in distributed quantum computing, opening up new possibilities for privacy-aware machine learning applications in the era of quantum technologies.

10.48550/arxiv.2310.12893

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Manipulating the particle-hole symmetry of quasiparticle bound states in geometric-size–varying Fe clusters on one-unit-cell FeSe/SrTiO₃(0 0 1)

Journal of Physics Condensed Matter (2019)

Chaofei Liu Guoqing Wang Jian Wang

The particle-hole symmetry (PHS) of quasiparticle bound states, which is generally expected in theory, is present or absent experimentally in a seemingly irregular manner, with the physical origin little understood yet. Here, we report a study on the bound states induced by Fe clusters with different sizes on one-unit-cell (1-UC) FeSe/SrTiO3(0 0 1) by in situ scanning tunneling spectroscopy. Statistically, on the larger-scale cluster, a pair of bias-symmetric minipeaks are detected within the superconducting-gap energies. As increasing temperature, the minipeak states show negligible energy dispersion. The temperature-independent bias-symmetric minipeaks are identified as the quasiparticle bound states that preserve the PHS. However, on the smaller-scale cluster, the bound state appears as a single resonance instead. These results reveal a geometric-size-tuning effect of the PHS, which may help reconcile the contradiction between the superconductivity theory and the PHS-breaking experiments.

10.1088/1361-648x/ab1630

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Citations (2)

Emulated nuclear spin gyroscope with 15N - V centers in diamond

Physical Review Applied (2024)

Guoqing Wang Minh-Thi Nguyen Dane W. deQuilettes E. Price Z. Hu

Nuclear spins in solid-state platforms are promising for building rotation sensors due to their long coherence times. Among these platforms, nitrogen-vacancy ($\mathrm{N}$-$V$) centers have attracted considerable attention with ambient operating conditions. However, the current performance of $\mathrm{N}$-$V$ gyroscopes remains limited by the degraded coherence when they are operating with large spin ensembles. Protecting the coherence of these systems requires a systematic study of the coherence-decay mechanism. Here we present the use of nitrogen-15 nuclear spins of $\mathrm{N}$-$V$ centers in building gyroscopes and compare their performance to the better studied nitroge-14 nuclear spins: while nitrogen-15 spins benefit from their simpler energy structure and lack of a quadrupolar interaction, they suffer from other challenges in coherence protection. We systematically reveal the coherence-decay mechanism of the nuclear spin in different $\mathrm{N}$-$V$ electronic spin manifolds and further develop a robust coherence-protection protocol based on controlling the $\mathrm{N}$-$V$ electronic spin only, achieving a 15-fold increase in dephasing time. With the coherence protection developed, we demonstrate an emulated gyroscope by measuring a designed rotation-rate pattern, showing an order-of-magnitude sensitivity improvement.

10.1103/physrevapplied.22.044016

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Orientation-independent room temperature optical ¹³ C hyperpolarization in powdered diamond

Science Advances (2018)

Ashok Ajoy Kristina Liu Raffi Nazaryan Xudong Lv Pablo R. Zangara

Shining light on diamond particles makes them MRI-“bright,” opening avenues for room temperature hyperpolarized liquids.

Hyperpolarization

10.1126/sciadv.aar5492

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Citations (70)

Manipulating solid-state spin concentration through charge transport

Proceedings of the National Academy of Sciences (2023)

Guoqing Wang Changhao Li Hao Tang Boning Li Francesca Madonini

Solid-state defects are attractive platforms for quantum sensing and simulation, e.g., in exploring many-body physics and quantum hydrodynamics. However, many interesting properties can be revealed only upon changes in the density of defects, which instead is usually fixed in material systems. Increasing the interaction strength by creating denser defect ensembles also brings more decoherence. Ideally one would like to control the spin concentration at will while keeping fixed decoherence effects. Here, we show that by exploiting charge transport, we can take some steps in this direction, while at the same time characterizing charge transport and its capture by defects. By exploiting the cycling process of ionization and recombination of NV centers in diamond, we pump electrons from the valence band to the conduction band. These charges are then transported to modulate the spin concentration by changing the charge state of material defects. By developing a wide-field imaging setup integrated with a fast single photon detector array, we achieve a direct and efficient characterization of the charge redistribution process by measuring the complete spectrum of the spin bath with micrometer-scale spatial resolution. We demonstrate a two-fold concentration increase of the dominant spin defects while keeping the

Charge carrier

10.1073/pnas.2305621120

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Citations (5)