The Experts below are selected from a list of 114411 Experts worldwide ranked by ideXlab platform
G D Forney - One of the best experts on this subject based on the ideXlab platform.
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optimal tight frames and Quantum Measurement
IEEE Transactions on Information Theory, 2002Co-Authors: Yonina C Eldar, G D ForneyAbstract:Tight frames and rank-one Quantum Measurements are shown to be intimately related. In fact, the family of normalized tight frames for the space in which a Quantum-mechanical system lies is precisely the family of rank-one generalized Quantum Measurements on that space. Using this relationship, frame-theoretical analogs of various Quantum-mechanical concepts and results are developed. The analog of a least-squares Quantum Measurement is a tight frame that is closest in a least-squares sense to a given set of vectors. The least-squares tight frame is found for both the case in which the scaling of the frame is specified (constrained least-squares frame (CLSF)) and the case in which the scaling is chosen to minimize the least-squares error (unconstrained least-squares frame (ULSF)). The well-known canonical frame is shown to be proportional to the ULSF and to coincide with the CLSF with a certain scaling.
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Optimal Tight Frames and Quantum Measurement
arXiv: Quantum Physics, 2001Co-Authors: Yonina C Eldar, G D ForneyAbstract:Tight frames and rank-one Quantum Measurements are shown to be intimately related. In fact, the family of normalized tight frames for the space in which a Quantum mechanical system lies is precisely the family of rank-one generalized Quantum Measurements (POVMs) on that space. Using this relationship, frame-theoretical analogues of various Quantum-mechanical concepts and results are developed. The analogue of a least-squares Quantum Measurement is a tight frame that is closest in a least-squares sense to a given set of vectors. The least-squares tight frame is found for both the case in which the scaling of the frame is specified (constrained least-squares frame (CLSF)) and the case in which the scaling is free (unconstrained least-squares frame (ULSF)). The well-known canonical frame is shown to be proportional to the ULSF and to coincide with the CLSF with a certain scaling. Finally, the canonical frame vectors corresponding to a geometrically uniform vector set are shown to be geometrically uniform and to have the same symmetries as the original vector set.
Yonina C Eldar - One of the best experts on this subject based on the ideXlab platform.
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optimal tight frames and Quantum Measurement
IEEE Transactions on Information Theory, 2002Co-Authors: Yonina C Eldar, G D ForneyAbstract:Tight frames and rank-one Quantum Measurements are shown to be intimately related. In fact, the family of normalized tight frames for the space in which a Quantum-mechanical system lies is precisely the family of rank-one generalized Quantum Measurements on that space. Using this relationship, frame-theoretical analogs of various Quantum-mechanical concepts and results are developed. The analog of a least-squares Quantum Measurement is a tight frame that is closest in a least-squares sense to a given set of vectors. The least-squares tight frame is found for both the case in which the scaling of the frame is specified (constrained least-squares frame (CLSF)) and the case in which the scaling is chosen to minimize the least-squares error (unconstrained least-squares frame (ULSF)). The well-known canonical frame is shown to be proportional to the ULSF and to coincide with the CLSF with a certain scaling.
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Optimal Tight Frames and Quantum Measurement
arXiv: Quantum Physics, 2001Co-Authors: Yonina C Eldar, G D ForneyAbstract:Tight frames and rank-one Quantum Measurements are shown to be intimately related. In fact, the family of normalized tight frames for the space in which a Quantum mechanical system lies is precisely the family of rank-one generalized Quantum Measurements (POVMs) on that space. Using this relationship, frame-theoretical analogues of various Quantum-mechanical concepts and results are developed. The analogue of a least-squares Quantum Measurement is a tight frame that is closest in a least-squares sense to a given set of vectors. The least-squares tight frame is found for both the case in which the scaling of the frame is specified (constrained least-squares frame (CLSF)) and the case in which the scaling is free (unconstrained least-squares frame (ULSF)). The well-known canonical frame is shown to be proportional to the ULSF and to coincide with the CLSF with a certain scaling. Finally, the canonical frame vectors corresponding to a geometrically uniform vector set are shown to be geometrically uniform and to have the same symmetries as the original vector set.
Andrew N. Jordan - One of the best experts on this subject based on the ideXlab platform.
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An Interaction-Free Quantum Measurement-Driven Engine
Foundations of Physics, 2020Co-Authors: Cyril Elouard, Mordecai Waegell, Benjamin Huard, Andrew N. JordanAbstract:Recently highly-efficient Quantum engines were devised by exploiting the stochastic energy changes induced by Quantum Measurement. Here we show that such an engine can be based on an interaction-free Measurement, in which the meter seemingly does not interact with the measured object. We use a modified version of the Elitzur–Vaidman bomb tester, an interferometric setup able to detect the presence of a bomb triggered by a single photon without exploding it. In our case, a Quantum bomb subject to a gravitational force is initially in a superposition of being inside and outside one of the interferometer arms. We show that the bomb can be lifted without blowing up. This occurs when a photon traversing the interferometer is detected at a port that is always dark when the bomb is located outside the arm. The required potential energy is provided by the photon (which plays the role of the meter) even though it was not absorbed by the bomb. A natural interpretation is that the photon traveled through the arm which does not contain the bomb—otherwise the bomb would have exploded—but it implies the surprising conclusion that the energy exchange occurred at a distance despite a local interaction Hamiltonian. We use the weak value formalism to support this interpretation and find evidence of contextuality. Regardless of interpretation, this interaction-free Quantum Measurement engine is able to lift the most sensitive bomb without setting it off.
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Quantum Measurement engines and their relevance for Quantum interpretations
Quantum Studies: Mathematics and Foundations, 2019Co-Authors: Andrew N. Jordan, Cyril Elouard, Alexia AuffèvesAbstract:This article presents recent progress in the theory of Quantum Measurement engines and discusses the implications of them for Quantum interpretations and philosophical implications of the theory. Several new Measurement engine designs are introduced and analyzed. We discuss a feedback-based atom-and-piston engine that exactly associates all work with successful events and all Quantum heat with the failed events, as well as an unconditional but coherent qubit engine that can attain perfect efficiency. Any Quantum Measurement of an observable that does not commute with the Hamiltonian will necessarily change the energy of the system. We discuss different ways to extract that energy, the efficiency and work production of that process.
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undoing a weak Quantum Measurement of a solid state qubit
Physical Review Letters, 2006Co-Authors: Alexander N Korotkov, Andrew N. JordanAbstract:We propose an experiment which demonstrates the undoing of a weak continuous Measurement of a solid-state qubit, so that any unknown initial state is fully restored. The undoing procedure has only a finite probability of success because of the nonunitary nature of Quantum Measurement, though it is accompanied by a clear experimental indication of whether or not the undoing has been successful. The probability of success decreases with increasing strength of the Measurement, reaching zero for a traditional projective Measurement. Measurement undoing (``Quantum undemolition'') may be interpreted as a kind of Quantum eraser, in which the information obtained from the first Measurement is erased by the second Measurement, which is an essential part of the undoing procedure. The experiment can be realized using Quantum dot (charge) or superconducting (phase) qubits.
Alexander N Korotkov - One of the best experts on this subject based on the ideXlab platform.
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decoherence suppression by Quantum Measurement reversal
Physical Review A, 2010Co-Authors: Alexander N Korotkov, Kyle KeaneAbstract:We show that qubit decoherence due to zero-temperature energy relaxation can be almost completely suppressed by using the Quantum uncollapsing (Measurement reversal) procedure. To protect a qubit state, a partial Quantum Measurement moves it toward the ground state, where it is kept during the storage period, while the second partial Measurement restores the initial state. This procedure preferentially selects the cases without energy decay events. Stronger decoherence suppression requires smaller selection probability; a desired point in this trade-off can be chosen by varying the Measurement strength. The experiment can be realized in a straightforward way using the superconducting phase qubit.
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undoing a weak Quantum Measurement of a solid state qubit
Physical Review Letters, 2006Co-Authors: Alexander N Korotkov, Andrew N. JordanAbstract:We propose an experiment which demonstrates the undoing of a weak continuous Measurement of a solid-state qubit, so that any unknown initial state is fully restored. The undoing procedure has only a finite probability of success because of the nonunitary nature of Quantum Measurement, though it is accompanied by a clear experimental indication of whether or not the undoing has been successful. The probability of success decreases with increasing strength of the Measurement, reaching zero for a traditional projective Measurement. Measurement undoing (``Quantum undemolition'') may be interpreted as a kind of Quantum eraser, in which the information obtained from the first Measurement is erased by the second Measurement, which is an essential part of the undoing procedure. The experiment can be realized using Quantum dot (charge) or superconducting (phase) qubits.
Yoonho Kim - One of the best experts on this subject based on the ideXlab platform.
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Emergence of the geometric phase from Quantum Measurement back-action
Nature Physics, 2019Co-Authors: Youngwook Cho, Yongsu Kim, Yosep Kim, Yeon-ho Choi, Sang-wook Han, Sang-yun Lee, Sung Moon, Yoonho KimAbstract:The state vector representing a Quantum system acquires a phase factor following an adiabatic evolution along a closed trajectory in phase space. This is the traditional example of a geometric phase, or Pancharatnam–Berry phase, a concept that has now been generalized beyond cyclic adiabatic evolutions to include generalized Quantum Measurements, and that has been experimentally measured in a variety of physical systems. However, a clear description of the relationship between the emergence of a geometric phase and the effects of a series of generalized Quantum Measurements on a Quantum system has not yet been provided. Here we report that a sequence of weak Measurements with continuously variable Measurement strengths in a Quantum optics experiment conclusively reveals that the Quantum Measurement back-action is the source of the geometric phase—that is, the stronger a Quantum Measurement, the larger the accumulated geometric phase. We furthermore find that in the limit of strong (projective) Measurement there is a direct connection between the geometric phase and the sequential weak value, ordinarily associated with a series of weak Quantum Measurements. Following a closed evolution in the Hilbert space, the state vector of a Quantum system accumulates a geometric phase factor. A series of weak Measurements reveal the origin of this in the back-action of any Quantum Measurement.
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protecting entanglement from decoherence using weak Measurement and Quantum Measurement reversal
Proceedings of SPIE, 2013Co-Authors: Yongsu Kim, Jongchan Lee, Osung Kwon, Yoonho KimAbstract:Decoherence, which causes degradation of entanglement and in some cases entanglement sudden death, is a critical issue faced in Quantum information. Protecting entanglement from decoherence, therefore, is essential in practical realization of Quantum computing and Quantum communication protocols. In this paper, we demonstrate a novel method to protect entanglement from amplitude damping decoherence via weak Measurement and Quantum Measurement reversal. It is shown that even entanglement sudden death can be circumvented.
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Reversing the weak Quantum Measurement for a photonic qubit
CLEO QELS: 2010 Laser Science to Photonic Applications, 2010Co-Authors: Yongsu Kim, Youngwook Cho, Yoonho KimAbstract:We demonstrate the conditional reversal of a weak Quantum Measurement on a photonic qubit. The state recovery fidelity, determined by Quantum process tomography, is shown to be over 94% for partial-collapse strength up to 0.9. We also experimentally study information gain due to the weak Measurement and discuss the role of the reversing operation as an information erasure.
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reversing the weak Quantum Measurement for a photonic qubit
arXiv: Quantum Physics, 2009Co-Authors: Yongsu Kim, Youngwook Cho, Yoonho KimAbstract:We demonstrate the conditional reversal of a weak (partial-collapse) Quantum Measurement on a photonic qubit. The weak Quantum Measurement causes a nonunitary transformation of a qubit which is subsequently reversed to the original state after a successful reversing operation. Both the weak Measurement and the reversal operation are implemented linear optically. The state recovery fidelity, determined by Quantum process tomography, is shown to be over 94% for partial-collapse strength up to 0.9. We also experimentally study information gain due to the weak Measurement and discuss the role of the reversing operation as an information erasure.
