Open Access. Powered by Scholars. Published by Universities.®

Quantum Physics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Chapman University

Discipline
Keyword
Publication Year
Publication
Publication Type

Articles 241 - 252 of 252

Full-Text Articles in Quantum Physics

Measuring Polynomial Invariants Of Multiparty Quantum States, Matthew S. Leifer, N. Linden, A. Winter Jan 2004

Measuring Polynomial Invariants Of Multiparty Quantum States, Matthew S. Leifer, N. Linden, A. Winter

Mathematics, Physics, and Computer Science Faculty Articles and Research

We present networks for directly estimating the polynomial invariants of multiparty quantum states under local transformations. The structure of these networks is closely related to the structure of the invariants themselves and this lends a physical interpretation to these otherwise abstract mathematical quantities. Specifically, our networks estimate the invariants under local unitary (LU) transformations and under stochastic local operations and classical communication (SLOCC). Our networks can estimate the LU invariants for multiparty states, where each party can have a Hilbert space of arbitrary dimension and the SLOCC invariants for multiqubit states. We analyze the statistical efficiency of our networks compared …

Go to article

Triplet Superconductors From The Viewpoint Of Basic Elements For Quantum Computers, Armen M. Gulian, Kent S. Wood Jul 2003

Triplet Superconductors From The Viewpoint Of Basic Elements For Quantum Computers, Armen M. Gulian, Kent S. Wood

Mathematics, Physics, and Computer Science Faculty Articles and Research

We discuss possibilities of utilizing superconductors with Cooper condensates in triplet pairing states (where the spin of condensate pairs is S=1) for practical realization of quantum computers. Superconductors with triplet pairing condensates have features that are unique and cannot be found in the usual (singlet pairing, S=0) superconductors. The symmetry of the order parameter in some triplet superconductors (e.g., ruthenates) corresponds to doubly-degenerate chiral states. These states can serve as qubit base states for quantum computing.

Go to article

Optimal Entanglement Generation From Quantum Operations, Matthew S. Leifer, L. Henderson, N. Linden Jan 2003

Optimal Entanglement Generation From Quantum Operations, Matthew S. Leifer, L. Henderson, N. Linden

Mathematics, Physics, and Computer Science Faculty Articles and Research

We consider how much entanglement can be produced by a nonlocal two-qubit unitary operation, UAB—the entangling capacity of UAB. For a single application of UAB , with no ancillas, we find the entangling capacity and show that it generally helps to act with UAB on an entangled state. Allowing ancillas, we present numerical results from which we can conclude, quite generally, that allowing initial entanglement typically increases the optimal capacity in this case as well. Next, we show that allowing collective processing does not increase the entangling capacity if initial entanglement is allowed.

Go to article

Experimental Quantum Cloning Of Single Photons, Antia Lamas-Linares, Christoph Simon, John C. Howell, Dik Bouwmeester Mar 2002

Experimental Quantum Cloning Of Single Photons, Antia Lamas-Linares, Christoph Simon, John C. Howell, Dik Bouwmeester

Mathematics, Physics, and Computer Science Faculty Articles and Research

Although perfect copying of unknown quantum systems is forbidden by the laws of quantum mechanics, approximate cloning is possible. A natural way of realizing quantum cloning of photons is by stimulated emission. In this context, the fundamental quantum limit to the quality of the clones is imposed by the unavoidable presence of spontaneous emission. In our experiment, a single input photon stimulates the emission of additional photons from a source on the basis of parametric down-conversion. This leads to the production of quantum clones with near-optimal fidelity. We also demonstrate universality of the copying procedure by showing that the same …

Go to article

Optimal Simulation Of Two-Qubit Hamiltonians Using General Local Operations, C. H. Bennett, J. I. Cirac, Matthew S. Leifer, D. W. Leung, N. Linden, S. Popescu, G. Vidal Jan 2002

Optimal Simulation Of Two-Qubit Hamiltonians Using General Local Operations, C. H. Bennett, J. I. Cirac, Matthew S. Leifer, D. W. Leung, N. Linden, S. Popescu, G. Vidal

Mathematics, Physics, and Computer Science Faculty Articles and Research

We consider the simulation of the dynamics of one nonlocal Hamiltonian by another, allowing arbitrary local resources but no entanglement or classical communication. We characterize notions of simulation, and proceed to focus on deterministic simulation involving one copy of the system. More specifically, two otherwise isolated systems A and B interact by a nonlocal Hamiltonian H≠HA+HB . We consider the achievable space of Hamiltonians H8 such that the evolution e2iH8t can be simulated by the interaction H interspersed with local operations. For any dimensions of A and B, and any nonlocal Hamiltonians H and H8, there exists a scale factor …

Go to article

Optically Simulating A Quantum Associative Memory, John C. Howell, John A. Yeazell, Dan Ventura Sep 2000

Optically Simulating A Quantum Associative Memory, John C. Howell, John A. Yeazell, Dan Ventura

Mathematics, Physics, and Computer Science Faculty Articles and Research

This paper discusses the realization of a quantum associative memory using linear integrated optics. An associative memory produces a full pattern of bits when presented with only a partial pattern. Quantum computers have the potential to store large numbers of patterns and hence have the ability to far surpass any classical neural-network realization of an associative memory. In this work two three-qubit associative memories will be discussed using linear integrated optics. In addition, corrupted, invented and degenerate memories are discussed.

Go to article

Quantum Computation Through Entangling Single Photons In Multipath Interferometers, John C. Howell, John A. Yeazell Jul 2000

Quantum Computation Through Entangling Single Photons In Multipath Interferometers, John C. Howell, John A. Yeazell

Mathematics, Physics, and Computer Science Faculty Articles and Research

Single-photon interferometry has been used to simulate quantum computations. Its use has been limited to studying few-bit applications due to rapid growth in physical size with numbers of bits. We propose a hybrid approach that employs n photons, each having L degrees of freedom yielding Ln basis states. The photons are entangled via a quantum nondemolition measurement. This approach introduces the essential element of quantum computing, that is, entanglement into the interferometry. Using these techniques, we demonstrate a controlled-NOT gate and a Grover's search circuit. These ideas are also applicable to the study of nonlocal correlations in many dimensions.

Go to article

Entangling Macroscopic Quantum States, John C. Howell, John A. Yeazell Jun 2000

Entangling Macroscopic Quantum States, John C. Howell, John A. Yeazell

Mathematics, Physics, and Computer Science Faculty Articles and Research

Spatial entanglements of macroscopic quantum systems are proposed. The which-path uncertainty of a single photon passing through a beam splitter is transformed into the which-path uncertainty of two macroscopic fields via two quantum nondemolition measurements. The macroscopic fields are nonlocally correlated.

Go to article

Reducing The Complexity Of Linear Optics Quantum Circuits, John C. Howell, John A. Yeazell Apr 2000

Reducing The Complexity Of Linear Optics Quantum Circuits, John C. Howell, John A. Yeazell

Mathematics, Physics, and Computer Science Faculty Articles and Research

Integrated optical elements can simplify the linear optics used to simulate quantum circuits. These linear optical simulations of quantum circuits have been developed primarily in terms of the free space optics associated with single-photon interferometry. For an L-bit simulation the number of required free-space optical elements is ∝2L if 50/50 beam splitters are used. The implementation (construction and alignment) of these circuits with these free-space elements is nontrivial. On the other hand, for the cases presented in this paper in which linear integrated optics (e.g., 2L×2L fiber couplers) are used, the number of optical devices does …

Go to article

Linear Optics Simulations Of The Quantum Baker’S Map, John C. Howell, John A. Yeazell Dec 1999

Linear Optics Simulations Of The Quantum Baker’S Map, John C. Howell, John A. Yeazell

Mathematics, Physics, and Computer Science Faculty Articles and Research

The unitary evolution of linear optics can be used to model quantum computational networks. In this paper, a quantum simulation of a classically chaotic map (the baker’s map) is developed using linear optics. Two different models are presented. The first model employs only 50-50 beam splitters and phase shifters to simulate universal 2-qubit gates of a quantum computer. The second model uses the discrete Fourier transform generated by symmetric N×N fiber couplers. If single photons are used as inputs for these linear optics models, the result is a physical realization of the quantum baker’s map.

Go to article

The Non-Local Universe: The New Physics And Matters Of The Mind, Robert Nadeau, Menas Kafatos Jan 1999

The Non-Local Universe: The New Physics And Matters Of The Mind, Robert Nadeau, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Books and Book Chapters

Classical physics states that physical reality is local, or that a measurement at one point in space cannot cannot influence what occurs at another beyond a fairly short distance. Until recently this seemed like an immutable truth in nature. However, in 1997 experiments were conducted in which light particles (photons) originated under certain conditions and traveled in opposite directions to detectors located about seven miles apart. The amazing results indicated that the photons "interacted" or "communicated" with one another instantly or "in no time," leading to the revelation that physical reality is non-local--a discovery that Robert Nadeau and Menas Kafatos …

Go to article

Yakir Aharonov Dissertation, Yakir Aharonov Jan 1960

Yakir Aharonov Dissertation, Yakir Aharonov

Faculty Collections

Yakir Aharonov's Dissertation entitled "Some Problems in the Quantum Theory of Measurements."

Go to article

First Prev