Welcome to the quantum precision measurement group at Key Lab of Quantum Information in University of Science and Technology of China (USTC). This group was established in Oct. 2010, and currently focuses on high precision measurement by harnessing quantum effects.

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PostDoc K. D. Wu’s recent work “Operational Resource Theory of Imaginarity” has been published on Physical Review Letter. DOI: https://doi.org/10.1103/PhysRevLett.126.090401

Associate researcher Z. B. Hou’s and research assistant Y. Jin’s work “Super-Heisenberg” and Heisenberg Scalings Achieved Simultaneously in the Estimation of a Rotating Field” has been published on Physical Review Letters.

We mainly focus on experimental quantum metrology and related technologies and fundamental physics such as quantum tomography, quantum resource theory, Heisenberg’s uncertainty relations and quantum correlations, which are detailed below. Our experimental works are mainly performed with linear photonics and photon-atom integrated chips.

Precision measurements are a major driving force of science and technology. The state-of-art traditional metrology has already reached its foundational ceiling, which is known as shot-noise limit. Fortunately, the next-generation quantum metrology, which utilizes quantum mechanical effects, such as superposition and entanglement, can increase the ceiling of precision up to Heisenberg limit. Although practical application scenarios involve many unknown parameters, general dynamics and noises, current studies mainly focus on the simplest single-parameter, commuting and noiseless cases such as phase estimation. To fill this gap between experimental studies and real application scenarios, we stand on the cutting edge of pushing experimental studies of quantum metrology towards multi-parameter [ 1], general non-commuting [ 2] and noisy cases.

Quantum tomography, characterizing the state of a quantum system, its evolution or measurement, is a starting point of many quantum information tasks. Precision and complexity are two main concerns of quantum tomography. Regarding to precision, we realized adaptive quantum tomography techniques [ 3] to achieve the quantum precision limit for individual measurements. To further improve the precision, we proposed and realized collective measurements using quantum walks, which achieved unprecedented precision and beat the precision limit of local measurements in quantum state tomography [ 4, 5]. Regarding to complexity of estimation algorithm, we proposed linear regression estimation and used parallel GPU programming to achieve full reconstruction of a 14-qubit state [ 5], the largest state ever fully reconstructed. We also experimentally self-guided tomography of a SU(2) operator to reduce the algorithm complexity of quantum process tomography [ 6]. Regarding to measurement complexity, we experimentally realized quantum process verification, which dramatically reduced the exponentially-increasing measurements to a polynomial growth of LOCC measurements.

Quantum resource theory studies the transformation and conversion of information under certain constrains. The quantification and manipulation of various resources are of central interest in quantum information, quantum thermodynamics, and other fields of physics. Recently, resource theories have inspired rigorous studies on the long-standing notions of non-classicality in localized systems, where the development of coherence theory has become a fundamental task. Here, we focus on both theoretical and experimental investigation on manipulating and converting quantum resources. In particular, we experimentally study the task of manipulating coherence in quantum states, put forward a circuit for cyclic inter-converting coherence and quantum correlations, develop a new method detecting non-Markovianity based on coherence, and experimentally test the power of collective measurement in reducing measurement backaction.

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