The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform

Poul S. Jessen - One of the best experts on this subject based on the ideXlab platform.

  • Quantum state tomography by Continuous Measurement and compressed sensing
    Physical Review A, 2013
    Co-Authors: Aaron Smith, Carlos Riofrio, Ivan H. Deutsch, Brian E. Anderson, H. Sosa-martinez, Poul S. Jessen
    Abstract:

    The need to perform quantum state tomography on ever larger systems has spurred a search for methods that yield good estimates from incomplete data. We study the performance of compressed sensing (CS) and least squares (LS) estimators in a fast protocol based on Continuous Measurement on an ensemble of cesium atomic spins. Both efficiently reconstruct nearly pure states in the 16-dimensional ground manifold, reaching average fidelities FCS = 0.92 and FLS = 0.88 using similar amounts of incomplete data. Surprisingly, the main advantage of CS in our protocol is an increased robustness to experimental imperfections

  • Quantum state reconstruction via Continuous Measurement.
    Physical review letters, 2005
    Co-Authors: Andrew Silberfarb, Poul S. Jessen, Ivan H. Deutsch
    Abstract:

    We present a new procedure for quantum state reconstruction based on weak Continuous Measurement of an ensemble average. By applying controlled evolution to the initial state, new information is continually mapped onto the measured observable. A Bayesian filter is then used to update the state estimate in accordance with the Measurement record. This generalizes the standard paradigm for quantum tomography based on strong, destructive Measurements on separate ensembles. This approach to state estimation induces minimal perturbation of the measured system, giving information about observables whose evolution cannot be described classically in real time and opening the door to new types of quantum feedback control.

Ivan H. Deutsch - One of the best experts on this subject based on the ideXlab platform.

  • Quantum state tomography by Continuous Measurement and compressed sensing
    Physical Review A, 2013
    Co-Authors: Aaron Smith, Carlos Riofrio, Ivan H. Deutsch, Brian E. Anderson, H. Sosa-martinez, Poul S. Jessen
    Abstract:

    The need to perform quantum state tomography on ever larger systems has spurred a search for methods that yield good estimates from incomplete data. We study the performance of compressed sensing (CS) and least squares (LS) estimators in a fast protocol based on Continuous Measurement on an ensemble of cesium atomic spins. Both efficiently reconstruct nearly pure states in the 16-dimensional ground manifold, reaching average fidelities FCS = 0.92 and FLS = 0.88 using similar amounts of incomplete data. Surprisingly, the main advantage of CS in our protocol is an increased robustness to experimental imperfections

  • Quantum state reconstruction via Continuous Measurement.
    Physical review letters, 2005
    Co-Authors: Andrew Silberfarb, Poul S. Jessen, Ivan H. Deutsch
    Abstract:

    We present a new procedure for quantum state reconstruction based on weak Continuous Measurement of an ensemble average. By applying controlled evolution to the initial state, new information is continually mapped onto the measured observable. A Bayesian filter is then used to update the state estimate in accordance with the Measurement record. This generalizes the standard paradigm for quantum tomography based on strong, destructive Measurements on separate ensembles. This approach to state estimation induces minimal perturbation of the measured system, giving information about observables whose evolution cannot be described classically in real time and opening the door to new types of quantum feedback control.

  • Continuous Measurement and the classical limit of the motion of an atom in a magneto-optical double-well potential
    Technical Digest. Summaries of papers presented at the Quantum Electronics and Laser Science Conference. Postconference Technical Digest (IEEE Cat. No, 1
    Co-Authors: S. Ghose, Ivan H. Deutsch, Kurt Jacobs, P.m. Alsing, Tanmoy Bhattacharya, Salman Habib
    Abstract:

    Summary form only given. The recovery of the classical limit in quantum systems that have underlying chaotic dynamics is a key question in current studies of the quantum to classical transition. Interaction with an environment results in decoherence that can cause the quantum Wigner function to approach the corresponding classical phase space distribution by suppressing quantum interference effects, but it fails to extract localized classical trajectories from the quantum dynamics. Such trajectories are crucial for quantifying chaos both theoretically and in experiments through the measure of the Lyapunov exponents. One can recover trajectories from the quantum dynamics through the process of Continuous Measurements when the record is retained. Ehrenfest s theorem guarantees that quantum systems that are well localized by the Measurement effectively obey classical mechanics. We have studied the role of Continuous Measurement in recovering the classical chaotic dynamics of laser cooled atoms in a magneto-optical lattice of double wells.

Alexander N. Korotkov - One of the best experts on this subject based on the ideXlab platform.

  • Bacon-Shor code with Continuous Measurement of noncommuting operators
    Physical Review A, 2017
    Co-Authors: Juan Atalaya, Mohammad Bahrami, Leonid P. Pryadko, Alexander N. Korotkov
    Abstract:

    We analyze the operation of a four-qubit Bacon-Shor code with simultaneous Continuous Measurement of non-commuting gauge operators. The error syndrome in this case is monitored via time-averaged cross-correlators of the output signals. We find the logical error rate for several models of decoherence, and also find the termination rate for this quantum error detecting code. The code operation is comparable to that based on projective Measurements when the collapse timescale due to Continuous Measurements is an order of magnitude less than the time period between the projective Measurements. An advantage of the Continuous-Measurement implementation is the absence of time-dependence in the code operation, with passive Continuous monitoring of the error syndrome.Comment: 25 pages, 8 figure

  • Continuous Measurement of entangled qubits
    Physical Review A, 2002
    Co-Authors: Alexander N. Korotkov
    Abstract:

    We have developed Bayesian formalism to describe the process of Continuous Measurement of entangled qubits. We start with the case of two qubits and then generalize it to an arbitrary number of qubits.

  • Selective quantum evolution of a qubit state due to Continuous Measurement
    Physical Review B, 2001
    Co-Authors: Alexander N. Korotkov
    Abstract:

    We consider a two-level quantum system (qubit) which is Continuously measured by a detector. The information provided by the detector is taken into account to describe the evolution during a particular realization of Measurement process. We discuss the Bayesian formalism for such ``selective'' evolution of an individual qubit and apply it to several solid-state setups. In particular, we show how to suppress the qubit decoherence using Continuous Measurement and the feedback loop.Comment: 15 pages (including 9 figures

Carlos Riofrio - One of the best experts on this subject based on the ideXlab platform.

  • Quantum state tomography by Continuous Measurement and compressed sensing
    Physical Review A, 2013
    Co-Authors: Aaron Smith, Carlos Riofrio, Ivan H. Deutsch, Brian E. Anderson, H. Sosa-martinez, Poul S. Jessen
    Abstract:

    The need to perform quantum state tomography on ever larger systems has spurred a search for methods that yield good estimates from incomplete data. We study the performance of compressed sensing (CS) and least squares (LS) estimators in a fast protocol based on Continuous Measurement on an ensemble of cesium atomic spins. Both efficiently reconstruct nearly pure states in the 16-dimensional ground manifold, reaching average fidelities FCS = 0.92 and FLS = 0.88 using similar amounts of incomplete data. Surprisingly, the main advantage of CS in our protocol is an increased robustness to experimental imperfections

  • Continuous Measurement Quantum State Tomography of Atomic Ensembles
    arXiv: Quantum Physics, 2011
    Co-Authors: Carlos Riofrio
    Abstract:

    Quantum state tomography is a fundamental tool in quantum information processing. It allows us to estimate the state of a quantum system by measuring different observables on many identically prepared copies of the system. This is, in general, a very time-consuming task that requires a large number of Measurements. There are, however, systems in which the data acquisition can be done more efficiently. In fact, an ensemble of quantum systems can be prepared and manipulated by external fields while being Continuously and collectively probed, producing enough information to estimate its state. This provides a basis for Continuous Measurement quantum tomography. In this protocol, an ensemble of identically prepared systems is collectively probed and controlled in a time-dependent manner to create an informationally complete Continuous Measurement record. The Measurement history is then inverted to determine the state at the initial time. We use two different estimation methods: maximum likelihood and compressed sensing. The general formalism is applied to the case of reconstruction of the quantum state encoded in the magnetic sub-levels of a large-spin alkali atom, ${}^{133}$Cs. We apply this protocol to the case of reconstruction of states in the full 16-dimensional electronic-ground subspace ($F=3 \oplus F=4$), controlled by microwaves and radio-frequency magnetic fields. We present an experimental demonstration of Continuous Measurement quantum tomography in an ensemble of cold cesium atoms with full control of its 16-dimensional Hilbert space. We show the exquisite level of control achieved in the lab and the excellent agreement between the theory discussed in this dissertation and the experimental results. This allows us to achieve fidelities >95% for low complexity quantum states, and >92% for arbitrary random states, which is a formidable accomplishment for a space of this size.

Aaron Smith - One of the best experts on this subject based on the ideXlab platform.

  • Quantum state tomography by Continuous Measurement and compressed sensing
    Physical Review A, 2013
    Co-Authors: Aaron Smith, Carlos Riofrio, Ivan H. Deutsch, Brian E. Anderson, H. Sosa-martinez, Poul S. Jessen
    Abstract:

    The need to perform quantum state tomography on ever larger systems has spurred a search for methods that yield good estimates from incomplete data. We study the performance of compressed sensing (CS) and least squares (LS) estimators in a fast protocol based on Continuous Measurement on an ensemble of cesium atomic spins. Both efficiently reconstruct nearly pure states in the 16-dimensional ground manifold, reaching average fidelities FCS = 0.92 and FLS = 0.88 using similar amounts of incomplete data. Surprisingly, the main advantage of CS in our protocol is an increased robustness to experimental imperfections