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The state of a continuously monitored qubit evolves stochastically, exhibiting competition between coherent Hamiltonian dynamics and diffusive partial collapse dynamics that follow the measurement record. We couple these distinct types of…

We present a formulation of feedback in quantum systems in which the best estimates of the dynamical variables are obtained continuously from the measurement record, and fed back to control the system. We apply this method to the problem of…

Quantum Physics · Physics 2009-10-31 A. C. Doherty , K. Jacobs

Active quantum error correction using qubit stabilizer codes has emerged as a promising, but experimentally challenging, engineering program for building a universal quantum computer. In this review we consider the formalism of qubit…

Quantum Physics · Physics 2015-04-13 Barbara M. Terhal

A five-qubit codeword stabilized quantum code is implemented in a seven-qubit system using nuclear magnetic resonance (NMR). Our experiment implements a good nonadditive quantum code which encodes a larger Hilbert space than any stabilizer…

Quantum Physics · Physics 2012-06-18 Jingfu Zhang , Markus Grassl , Bei Zeng , Raymond Laflamme

Entanglement generation can be robust against noise in approaches that deliberately incorporate dissipation into the system dynamics. The presence of additional dissipation channels may, however, limit fidelity and speed of the process.…

Quantum Physics · Physics 2019-01-28 Karl P. Horn , Florentin Reiter , Yiheng Lin , Dietrich Leibfried , Christiane P. Koch

Remote entanglement of distant, non-interacting quantum entities is a key primitive for quantum information processing. We present a new protocol to remotely entangle two stationary qubits by first entangling them with propagating ancilla…

Quantum Physics · Physics 2017-12-11 Ananda Roy , A. Douglas Stone , Liang Jiang

We demonstrate by an explicit model calculation that the decay of entanglement of two two-state systems (two qubits) is governed by the product of the factors that measure the degree of decoherence of each of the qubits, subject to…

Quantum Physics · Physics 2010-10-12 D. Tolkunov , V. Privman , P. K. Aravind

We investigate the decay of entanglement, due to decoherence, of multi-qubit systems that are initially prepared in highly (in some cases maximally) entangled states. We assume that during the decoherence processes each qubit of the system…

Quantum Physics · Physics 2009-11-13 A. Borras , A. P. Majtey , A. R. Plastino , M. Casas , A. Plastino

Quantum mechanics dictates the band-structure of materials that is essential for functional electronic components. With increased miniaturization of devices, it becomes possible to exploit the full potential of quantum mechanics through the…

Quantum Physics · Physics 2022-05-26 Kasper Poulsen , Alan C. Santos , Lasse B. Kristensen , Nikolaj T. Zinner

Conditional measurements on the undriven mode of a two-mode cavity QED system prepare a coherent superposition of ground states which generate quantum beats. The continuous system drive induces decoherence through the phase interruptions…

We introduce an experimental procedure for the detection of quantum entanglement of an unknown quantum state with as few measurements as possible. The method requires neither a priori knowledge of the state nor a shared reference frame…

We consider the problem of stabilizing the coherence of a single qubit subject to Markovian decoherence, via the application of a control Hamiltonian, without any additional resources. In this case neither quantum error…

Quantum Physics · Physics 2007-05-23 Daniel A. Lidar , Sara Schneider

We propose active steering protocols for quantum state preparation in quantum circuits where each system qubit is connected to a single detector qubit, employing a simple coupling selected from a small set of steering operators. The…

Quantum Physics · Physics 2024-03-07 Samuel Morales , Yuval Gefen , Igor Gornyi , Alex Zazunov , Reinhold Egger

Protecting quantum information from errors is essential for large-scale quantum computation. Quantum error correction (QEC) encodes information in entangled states of many qubits, and performs parity measurements to identify errors without…

Long-range entangled states are vital for quantum information processing and quantum metrology. Preparing such states by combining measurements with unitary gates opened new possibilities for efficient protocols with finite-depth quantum…

Quantum Physics · Physics 2024-08-07 Iosifina Angelidi , Marcin Szyniszewski , Arijeet Pal

Quantum computers require error correction to achieve universal quantum computing. However, current decoding of quantum error-correcting codes relies on classical computation, which is slower than quantum operations in superconducting…

Quantum Physics · Physics 2025-06-11 Pan Zhang

Large-scale quantum computers will inevitably need quantum error correction (QEC) to protect information against decoherence. Given that the overhead of such error correction is often formidable, autonomous quantum error correction (AQEC)…

Quantum Physics · Physics 2024-01-11 Ziqian Li , Tanay Roy , David Rodríguez Pérez , David I. Schuster , Eliot Kapit

Scalable quantum information processing requires the ability to tune multi-qubit interactions. This makes the precise manipulation of quantum states particularly difficult for multi-qubit interactions because tunability unavoidably…

We address the standard quantum error correction using the three-qubit bit-flip code, yet in continuous-time. This entails rendering a target manifold of quantum states globally attractive. Previous feedback designs could feature spurious…

Quantum Physics · Physics 2019-06-18 Gerardo Cardona , Alain Sarlette , Pierre Rouchon

We propose a time-delayed feedback control scheme for open quantum systems that can dramatically reduce the time to reach steady state. No measurement is performed in the feedback loop, and we suggest a simple all-optical implementation for…

Quantum Physics · Physics 2014-08-27 A L Grimsmo , A S Parkins , B-S Skagerstam