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A central task in quantum information science is state certification: testing whether an unknown state is $\epsilon_1$-close to a fixed target state, or $\epsilon_2$-far. Recent work has shown that surprisingly simple measurement…

Quantum Physics · Physics 2026-02-13 Andrea Coladangelo , Jerry Li , Joseph Slote , Ellen Wu

When measuring phase of quantum states of light, the optimal single-shot measurement implements projection on the un-physical phase states. If we want to improve the precision further we need to accept a reduced probability of success,…

Quantum Physics · Physics 2015-06-16 Petr Marek

We propose a quantum tomography scheme for pure qudit systems which adopts random base measurements and generative learning methods, along with a built-in fidelity estimation approach to assess the reliability of the tomographic states. We…

Quantum Physics · Physics 2020-03-25 Jun Wang , Zhao-Yu Han , Song-Bo Wang , Zeyang Li , Liang-Zhu Mu , Heng Fan , Lei Wang

Real quantum measurements almost always cause a much stronger back action than required by the laws of quantum mechanics. In particular, free-space optical detection methods for single atoms and ions such as the shelving technique, though…

Quantum Physics · Physics 2011-06-10 Jürgen Volz , Roger Gehr , Guilhem Dubois , Jérôme Estève , Jakob Reichel

Quantum entanglement is the key resource for quantum information processing. Device-independent certification of entangled states is a long standing open question, which arouses the concept of self-testing. The central aim of self-testing…

Experimentally achieving the precision that standard quantum metrology schemes promise is always challenging. Recently, additional controls were applied to design feasible quantum metrology schemes. However, these approaches generally does…

Quantum Physics · Physics 2020-07-22 Xiaodong Yang , Jayne Thompson , Ze Wu , Mile Gu , Xinhua Peng , Jiangfeng Du

In this work, we consider the fundamental task of quantum state certification: given copies of an unknown quantum state $\rho$, test whether it matches some target state $\sigma$ or is $\epsilon$-far from it. For certifying $d$-dimensional…

Quantum Physics · Physics 2026-04-10 Chirag Wadhwa , Sitan Chen

Certifying that an n-qubit state synthesized in the lab is close to the target state is a fundamental task in quantum information science. However, existing rigorous protocols either require deep quantum circuits or exponentially many…

Quantum Physics · Physics 2024-04-12 Hsin-Yuan Huang , John Preskill , Mehdi Soleimanifar

Two-qubit systems typically employ 36 projective measurements for high-fidelity tomographic estimation. The overcomplete nature of the 36 measurements suggests possible robustness of the estimation procedure to missing measurements. In this…

Quantum Physics · Physics 2020-12-08 Onur Danaci , Sanjaya Lohani , Brian T. Kirby , Ryan T. Glasser

We investigate optimal discrimination between two projective single-qubit measurements in a scenario where the measurement can be performed only once. We consider general setting involving a tunable fraction of inconclusive outcomes and we…

Quantum Physics · Physics 2014-12-01 M. Mikova , M. Sedlak , I. Straka , M. Micuda , M. Ziman , M. Jezek , M. Dusek , J. Fiurasek

Conditional quantum optical processes enable a wide range of technologies from generation of highly non-classical states to implementation of quantum logic operations. The process fidelity that can be achieved in a realistic implementation…

Quantum Physics · Physics 2015-06-23 Merlin Cooper , Eirion Slade , Michal Karpinski , Brian J. Smith

Quantum fidelity is a measure to quantify the closeness of two quantum states. In an operational sense, it is defined as the minimal overlap between the probability distributions of measurement outcomes and the minimum is taken over all…

Quantum Physics · Physics 2019-07-24 Changhun Oh , Changhyoup Lee , Leonardo Banchi , Su-Yong Lee , Carsten Rockstuhl , Hyunseok Jeong

Quantum illumination is a protocol for detecting a low-reflectivity target by using two-mode entangled states composed of signal and idler modes, which can outperform unentangled states. We study multi-qudit states for single-shot detection…

Quantum Physics · Physics 2026-01-01 Sunghwa Kang , Yonggi Jo , Jihwan Kim , Zaeill Kim , Duk Y. Kim , Su-Yong Lee

We experimentally investigate a strategy to discriminate between quaternary phase-shift keyed coherent states based on single-shot measurements that is compatible with high-bandwidth communications. We extend previous theoretical work in…

Quantum Physics · Physics 2018-03-21 M. T. DiMario , E. Carrasco , R. A. Jackson , F. E. Becerra

The ability of quantum computers to directly manipulate and analyze quantum states stored in quantum memory allows them to learn about aspects of our physical world that would otherwise be invisible given a modest number of measurements.…

Quantum Physics · Physics 2024-12-10 Robbie King , Kianna Wan , Jarrod McClean

Conventionally, unknown quantum states are characterized using quantum-state tomography based on strong or weak measurements carried out on an ensemble of identically prepared systems. By contrast, the use of protective measurements offers…

Quantum Physics · Physics 2016-01-25 Maximilian Schlosshauer

We give a pair of algorithms that efficiently learn a quantum state prepared by Clifford gates and $O(\log n)$ non-Clifford gates. Specifically, for an $n$-qubit state $|\psi\rangle$ prepared with at most $t$ non-Clifford gates, our…

Quantum Physics · Physics 2025-11-07 Sabee Grewal , Vishnu Iyer , William Kretschmer , Daniel Liang

Optimal quantum cloning is the process of making one or more copies of an arbitrary unknown input quantum state with the highest possible fidelity. All reported demonstrations of quantum cloning have so far been limited to copying…

Quantum metrology uses quantum states with no classical counterpart to measure a physical quantity with extraordinary sensitivity or precision. Most metrology schemes measure a single parameter of a dynamical process by probing it with a…

Quantum Physics · Physics 2014-11-11 Lee A. Rozema , Dylan H. Mahler , Robin Blume-Kohout , Aephraim M. Steinberg

In this paper we address the problem of optimal reconstruction of a quantum state from the result of a single measurement when the original quantum state is known to be a member of some specified set. A suitable figure of merit for this…

Quantum Physics · Physics 2007-05-23 Kieran Hunter , Erika Andersson , Claire R. Gilson , Stephen M. Barnett
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