A5038980216- Quantum Information and Cryptography
- Quantum Mechanics and Applications
- Quantum Computing Algorithms and Architecture
- Quantum optics and atomic interactions
- Photonic and Optical Devices
- Mechanical and Optical Resonators
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Fiber Laser Technologies
- Advanced Optical Sensing Technologies
- Orbital Angular Momentum in Optics
- Neural Networks and Reservoir Computing
- Laser-Matter Interactions and Applications
- Atomic and Subatomic Physics Research
- Biofield Effects and Biophysics
- Ocular and Laser Science Research
- Optical Network Technologies
- Photorefractive and Nonlinear Optics
- Advanced Thermodynamics and Statistical Mechanics
- Quantum and electron transport phenomena
- Random lasers and scattering media
- Advanced Fluorescence Microscopy Techniques
- Quantum Electrodynamics and Casimir Effect
- Radiation Detection and Scintillator Technologies
- Chaos-based Image/Signal Encryption
- Semiconductor Lasers and Optical Devices
University of Illinois Urbana-Champaign
2016-2025
University of Illinois System
2004-2024
Urbana University
2002-2022
University of Patras
2022
Los Alamos National Laboratory
1996-2005
The University of Queensland
2000-2005
Executive Office of the President
2000
University of California Office of the President
2000
University of California System
1987-1999
Los Alamos Medical Center
1999
We report on a high-intensity source of polarization-entangled photon pairs with high momentum definition. Type-II noncollinear phase matching in parametric down conversion produces true entanglement: No part the wave function must be discarded, contrast to previous schemes. With two-photon fringe visibilities excess 97%, we demonstrated violation Bell's inequality by over 100 standard deviations less than 5 min. The new allowed ready preparation all four EPR-Bell states.
We describe in detail the theory underpinning measurement of density matrices a pair quantum two-level systems (``qubits''). Our particular emphasis is on qubits realized by two polarization degrees freedom entangled photons generated down-conversion experiment; however, discussion applies general, regardless actual physical realization. Two techniques are discussed, namely, tomographic reconstruction (in which matrix linearly related to set measured quantities) and maximum likelihood...
We have detected a spin-dependent displacement perpendicular to the refractive index gradient for photons passing through an air-glass interface. The effect is photonic version of spin Hall in electronic systems, indicating universality particles different nature. Treating as weak measurement projection photons, we used preselection and postselection technique on state enhance original by nearly four orders magnitude, attaining sensitivity displacements approximately 1 angstrom. can be...
Classically, sending more than one bit of information requires manipulation two-state particle. We demonstrate experimentally that can transmit three messages, i.e., 1 ``trit'' $\ensuremath{\approx}1.58\mathrm{bit}$, by manipulating only two entangled particles. The increased channel capacity is proven transmitting ASCII characters in five trits instead the usual 8 bits.
We present a loophole-free violation of local realism using entangled photon pairs. ensure that all relevant events in our Bell test are spacelike separated by placing the parties far enough apart and fast random number generators high-speed polarization measurements. A high-quality polarization-entangled source photons, combined with high-efficiency, low-noise, single-photon detectors, allows us to make measurements without requiring any fair-sampling assumptions. Using hypothesis test, we...
Using the process of spontaneous parametric down conversion in a novel two-crystal geometry, one can generate source polarization-entangled photon pairs which is orders magnitude brighter than previous sources. We have measured high level entanglement between photons emitted over relatively large collection angle, and 10-nm bandwidth. As demonstration intensity, we obtained 242-$\sigma$ violation Bell's inequalities less three minutes.
Using a two-photon interferometer, we have measured the time delay for photon to tunnel across barrier consisting of 1.1-\ensuremath{\mu}m-thick 1D photonic band-gap material. The peak wave packet appears on far side 1.47\ifmmode\pm\else\textpm\fi{}0.21 fs earlier than it would if were travel at vacuum speed light c. Although apparent tunneling velocity (1.7\ifmmode\pm\else\textpm\fi{}0.2)c is superluminal, this not genuine signal velocity, and Einstein causality violated. consistent with...
We experimentally demonstrate the first quantum system entangled in every degree of freedom (hyperentangled). Using pairs photons produced spontaneous parametric down-conversion, we verify entanglement by observing a Bell-type inequality violation each freedom: polarization, spatial mode, and time energy. also produce characterize maximally hyperentangled states novel simultaneously exhibiting both classical correlations. Finally, report tomography 2 x 3 (36-dimensional Hilbert space), which...
We show that one can ascertain the presence of an object in some sense without interacting with it. One repeatedly, but weakly, tests for object, which would inhibit otherwise coherent evolution interrogating photon. The fraction ``interaction-free'' measurements be arbitrarily close to 1. Using single photons a Michelson interferometer, we have performed preliminary demonstration these ideas.
Using spontaneous parametric down-conversion, we produce polarization-entangled states of two photons and characterize them using two-photon tomography to measure the density matrix. A controllable decoherence is imposed on by passing through thick, adjustable birefringent elements. When system subject collective decoherence, one particular entangled state seen be decoherence-free, as predicted theory. Such decoherence-free systems may have an important role for future quantum computation...
Using a spontaneous-downconversion photon source, we produce true non-maximally entangled states, i.e., without the need for post-selection. The degree and phase of entanglement are readily tunable, characterized both by standard analysis using coincidence minima, quantum state tomography two-photon state. latter, experimentally reconstruct reduced density matrix polarization. Finally, use these states to measure Hardy fraction, obtaining result that is $122 \sigma$ from any local-realistic result.
We present a source of entangled photons that violates Bell inequality free the "fair-sampling" assumption, by over 7 standard deviations. This violation is first reported experiment with to close detection loophole, and we demonstrate enough "efficiency" overhead eventually perform fully loophole-free test local realism. The entanglement quality verified maximally violating additional tests, testing upper limit quantum correlations. Finally, use generate "device-independent" private random...
Quantum teleportation faces increasingly demanding requirements for transmitting large or even entangled systems. However, knowledge of the state to be transmitted eases its reconstruction, resulting in a protocol known as remote preparation. A number experimental demonstrations date have been restricted single-qubit We report preparation two-qubit ``hybrid'' states, including family vector-polarization beams. Our single-photon states are encoded photon spin and orbital angular momentum....
Get PDF Email Share with Facebook Tweet This Post on reddit LinkedIn Add to CiteULike Mendeley BibSonomy Citation Copy Text L. K. Shalm, E. Meyer-Scott, B. G. Christensen, P. Bierhorst, M. A. Wayne, J. Stevens, T. Gerrits, S. Glancy, D. R. Hamel, Allman, Coakley, Dyer, C. Hodge, Lita, V. Verma, Lambrocco, Tortorici, Migdall, Y. Zhang, Kumor, W. H. Farr, F. Marsili, Shaw, Stern, Abellán, Amaya, Pruneri, Jennewein, Mitchell, Kwiat, Bienfang, Mirin, Knill, and Nam, "A strong loophole-free test...
Time multiplexing with a low-loss adjustable optical delay line enables largely enhanced emissions of heralded single photons.
Using polarization-entangled photons from spontaneous parametric down-conversion, we have implemented Ekert's quantum cryptography protocol. The near-perfect correlations of the allow sharing a secret key between two parties. presence an eavesdropper is continually checked by measuring Bell's inequalities. We investigated several possible strategies, including pseudo--quantum-nondemolition measurements. In all cases, eavesdropper's was readily apparent. discuss procedure to increase her...
We present various experiments demonstrating the mutual exclusivity of observing interference and which-path information, as demanded by Bohr's complementarity principle. Using photon pairs created in parametric down-conversion, no measurements need to be performed on interfering itself. Instead other can used introduce distinguishability, which consequently destroys interference. However, a suitable measurement erases this distinguishability recovered.
We report on a two-photon interference experiment proposed by Franson [Phys. Rev. Lett. 62, 2205 (1989)], in which sinusoidal fringes with visibilities greater than 70.7%, such as those predicted quantum mechanics, violate Bell inequality. observe visibility of 80.4\ifmmode\pm\else\textpm\fi{}0.6%, implying violation the inequality 16 standard deviations. Here elements reality under consideration are energy and time rather spin components. Any classical field models describing separate beams...
Complete and precise characterization of a quantum dynamical process can be achieved via the method tomography. Using source correlated photons, we have implemented several methods, each investigating wide range processes, e.g., unitary, decohering, polarizing. One these ancilla-assisted tomography (AAPT), makes use an additional "ancilla system," theoretically determined conditions when AAPT is possible. Surprisingly, entanglement not required. We present data obtained using both separable...
A constructive method for simulating small-scale quantum circuits by use of linear optical devices is presented. It relies on the representation several bits a single photon, and implementation universal gates using simple components (beam splitters, phase shifters, etc.). This suggests that realization small networks with present-day optics technology reasonable goal. technique could be useful demonstrating basic concepts algorithms or error-correction schemes. The analog nontrivial...
Abstract Entangled states are key ingredients to the new field of quantum information, including dense coding, teleportation, and computation. However, only a relatively small class entangled has been investigated experimentally, or even discussed extensively. In particular, efforts date have focused on two particles in single degree freedom, for example polarization, energy, momentum direction. Novel phase-matching arrangements spontaneous parametric down-conversion allow preparation pairs...
Two-qubit states occupy a large and relatively unexplored Hilbert space. Such can be succinctly characterized by their degree of entanglement purity. In this article we investigate entangled mixed present class that have the maximum amount for given linear entropy.