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Precise quantum control and measurement of several harmonic oscillators, such as the modes of the electromagnetic field in a cavity or of mechanical motion, are key for their use as quantum platforms. The motional modes of trapped ions can…

Quantum computers require high-fidelity measurement of many qubits to achieve a quantum advantage. Traditional approaches suffer from readout crosstalk for a neutral-atom quantum processor with a tightly spaced array. Although classical…

We propose a classification of measurement apparatuses based on their reliability and accessibility. Our notion of reliability parameterises the possibility of getting unexpected wrong results when using the apparatus in a given time…

Quantum Physics · Physics 2024-07-26 Nicola Pranzini , Paola Verrucchi

Quantum error correction of a surface code or repetition code requires the pairwise matching of error events in a space-time graph of qubit measurements, such that the total weight of the matching is minimized. The input weights follow from…

Quantum Physics · Physics 2018-08-01 S. T. Spitz , B. Tarasinski , C. W. J. Beenakker , T. E. O'Brien

Quantum Fourier transform (QFT) is a key ingredient of many quantum algorithms where a considerable amount of ancilla qubits and gates are often needed to form a Hilbert space large enough for high-precision results. Qubit recycling reduces…

This letter generalizes the expression for the average fidelity of single qubits, as found by Bowdrey et al., to the case of n qubits. We use a simple algebraic approach with basis elements for the density-matrix expansion expressed as…

Quantum Physics · Physics 2009-11-13 R. Cabrera , W. E. Baylis

Optical atomic clocks based on trapped ions suffer from systematic frequency shifts of the clock transition due to interaction with blackbody radiation from the environment. These shifts can be compensated if the blackbody radiation…

Atomic Physics · Physics 2024-10-11 Fabian Wolf

High fidelity qubit readout is a cornerstone for quantum information protocols. In traditional superconducting qubit readout, a chain of microwave amplifiers and nonreciprocal components aid in detecting the qubit's state with tolerable…

Quantum Physics · Physics 2026-03-16 B. T. Miller , Lindsay Orr , A. Metelmann , F. Lecocq

Quantum enhanced receivers are endowed with resources to achieve higher sensitivities than conventional technologies. For application in optical communications, they provide improved discriminatory capabilities for multiple non-orthogonal…

Quantum machine learning seeks to leverage quantum computers to improve upon classical machine learning algorithms. Currently, robust uncertainty quantification methods remain underdeveloped in the quantum domain, despite the critical need…

Machine Learning · Computer Science 2026-05-18 Douglas Spencer , Samual Nicholls , Michele Caprio

We show how high fidelity quantum teleportation of light to atoms can be achieved in the same setup as was used in the recent experiment [J. Sherson et.al., quant-ph/0605095, accepted by Nature], where such an inter-species quantum state…

Quantum Physics · Physics 2007-05-23 K. Hammerer , E. S. Polzik , J. I. Cirac

Measurement-induced state disturbance is a major challenge in obtaining quantum statistics at multiple time points. We propose a method to extract dynamic information from a quantum system at intermediate time points, namely snapshotting…

We compare and contrast the error probability and fidelity as measures of the quality of the receiver's measurement strategy for a quantum communications system. The error probability is a measure of the ability to retrieve {\it classical}…

Quantum Physics · Physics 2009-11-07 Stephen M. Barnett , Claire R. Gilson , Masahide Sasaki

We demonstrate that the coherence of a single mobile atomic qubit can be well preserved during a transfer process among different optical dipole traps (ODTs). This is a prerequisite step in realizing a large-scale neutral atom quantum…

The measurement of a superconducting qubit is implemented by coupling it to a resonator. The common choice is transverse coupling, which, in the dispersive approximation, introduces an interaction term which enables the measurement. This…

Quantum Physics · Physics 2025-01-30 Kishor V. Salunkhe , Suman Kundu , Srijita Das , Jay Deshmukh , Meghan P. Patankar , R. Vijay

We consider the multi-qubit fixed-excitation state transfer along the spin chain with dipole-dipole interaction subjected to the interaction with environment governed by the Lindblad equation preserving the excitation number during…

Quantum Physics · Physics 2026-05-14 E. B. Fel'dman , A. I. Zenchuk

We propose a Quantum Non Demolition (QND) read-out scheme for a superconducting artificial atom coupled to a resonator in a circuit QED architecture, for which we estimate a very high measurement fidelity without Purcell effect limitations.…

Quantum Physics · Physics 2015-06-15 I. Diniz , E. Dumur , O. Buisson , A. Auffèves

We propose the scheme implementing partial deterministic non-demolition Bell measurement. When it is used in quantum teleportation the information about an unknown input state is optimally distributed among three outgoing qubits. The…

Quantum Physics · Physics 2007-05-23 Ladislav Mišta , Radim Filip

We study how the spontaneous relaxation of a qubit affects a continuous quantum non-demolition measurement of the initial state of the qubit. Given some noisy measurement record $\Psi$, we seek an estimate of whether the qubit was initially…

Mesoscale and Nanoscale Physics · Physics 2009-11-13 Jay Gambetta , W. A. Braff , A. Wallraff , S. M. Girvin , R. J. Schoelkopf

In a quantum network, a key challenge is to minimize the direct reflection of flying qubits as they couple to stationary, resonator-based memory qubits, as the reflected amplitude represents state transfer infidelity that cannot be directly…

Quantum Physics · Physics 2020-11-12 Eric Chatterjee , Daniel Soh , Matt Eichenfield