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Lundeen JS, Steinberg AM. Experimental joint weak measurement on a photon pair as a probe of Hardy's paradox. PHYSICAL REVIEW LETTERS 2009; 102:020404. [PMID: 19257252 DOI: 10.1103/physrevlett.102.020404] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2008] [Indexed: 05/27/2023]
Abstract
It has been proposed that the ability to perform joint weak measurements on postselected systems would allow us to study quantum paradoxes. These measurements can investigate the history of those particles that contribute to the paradoxical outcome. Here we experimentally perform weak measurements of joint (i.e., nonlocal) observables. In an implementation of Hardy's paradox, we weakly measure the locations of two photons, the subject of the conflicting statements behind the paradox. Remarkably, the resulting weak probabilities verify all of these statements but, at the same time, resolve the paradox.
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Affiliation(s)
- J S Lundeen
- Department of Physics, University of Toronto, 60 St. George Street, Toronto ON, M5S 1A7, Canada
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Zhang J, Hernandez G, Zhu Y. Optical switching mediated by quantum interference of Raman transitions. OPTICS EXPRESS 2008; 16:19112-19117. [PMID: 19582003 DOI: 10.1364/oe.16.019112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We report an experimental study of quantum interference between two-photon Raman transitions and demonstration of the phase control of light attenuation/transmission in cold Rb atoms. By varying the phase and frequency of a weak control laser, either constructive interference or destructive interference between the two-photon Raman transitions in a three-level Lambda system can be manipulated. The interference enables absorptive switching of one field by another field at low light levels.
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Affiliation(s)
- Jiepeng Zhang
- Department of Physics, Florida International University, Miami, FL 33199, USA
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Zhang J, Hernandez G, Zhu Y. All-optical switching at ultralow light levels. OPTICS LETTERS 2007; 32:1317-9. [PMID: 17440573 DOI: 10.1364/ol.32.001317] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We report an experimental demonstration of all-optical switching at ultralow light levels in coherently prepared Rb atoms. A signal light pulse is switched on and off by a control light pulse at different frequencies in a four-level atomic system based on multiphoton interferences. We observed a switching efficiency of 55% with the signal and control light pulses containing approximately 20 photons each, corresponding to a control energy density of approximately 10(-5) photons per atomic cross section lambda(2)/(2pi).
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Affiliation(s)
- Jiepeng Zhang
- Department of Physics, Florida International University, Miami, Florida 33199, USA
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Agarwal GS. Interferences in parametric interactions driven by quantized fields. PHYSICAL REVIEW LETTERS 2006; 97:023601. [PMID: 16907440 DOI: 10.1103/physrevlett.97.023601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2006] [Indexed: 05/11/2023]
Abstract
We report interferences in the quantum fluctuations of the output of a parametric amplifier when the cavity is driven by a quantized field at the signal frequency. The interferences depend on the phase fluctuations of the input quantized field and result in splitting of the spectrum of the output, and thus the recent observation [H. Ma, Phys. Rev. Lett. 95, 233601 (2005)10.1103/PhysRevLett.95.233601] of interferences in the classical domain have a very interesting counterpart in the quantum domain. The interferences can be manipulated, for example, by changing the amount of squeezing in the input field.
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Affiliation(s)
- G S Agarwal
- Department of Physics, Oklahoma State University, Stillwater, 74078, USA
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Dayan B, Pe'er A, Friesem AA, Silberberg Y. Nonlinear interactions with an ultrahigh flux of broadband entangled photons. PHYSICAL REVIEW LETTERS 2005; 94:043602. [PMID: 15783557 DOI: 10.1103/physrevlett.94.043602] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2004] [Indexed: 05/24/2023]
Abstract
We experimentally demonstrate sum-frequency generation with entangled photon pairs, generating as many as 40,000 photons per second, visible even to the naked eye. The nonclassical nature of the interaction is exhibited by a linear intensity dependence of the nonlinear process. The key element in our scheme is the generation of an ultrahigh flux of entangled photons while maintaining their nonclassical properties. This is made possible by generating the down-converted photons as broadband as possible, orders of magnitude wider than the pump. This approach can be applied to other nonlinear interactions, and may become useful for various quantum-measurement tasks.
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Affiliation(s)
- Barak Dayan
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel
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Resch KJ, Steinberg AM. Extracting joint weak values with local, single-particle measurements. PHYSICAL REVIEW LETTERS 2004; 92:130402. [PMID: 15089586 DOI: 10.1103/physrevlett.92.130402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2003] [Indexed: 05/24/2023]
Abstract
Weak measurement is a new technique which allows one to describe the evolution of postselected quantum systems. It appears to be useful for resolving a variety of thorny quantum paradoxes, particularly when used to study properties of pairs of particles. Unfortunately, such nonlocal or joint observables often prove difficult to measure directly in practice (for instance, in optics-a common testing ground for this technique-strong photon-photon interactions would be needed to implement an appropriate von Neumann interaction). Here we derive a general, experimentally feasible, method for extracting these joint weak values from correlations between single-particle observables.
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Affiliation(s)
- K J Resch
- Institut für Experimentalphysik, Universität Wien, Boltzmanngasse 5, A-1090 Vienna, Austria
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Mohseni M, Lundeen JS, Resch KJ, Steinberg AM. Experimental application of decoherence-free subspaces in an optical quantum-computing algorithm. PHYSICAL REVIEW LETTERS 2003; 91:187903. [PMID: 14611316 DOI: 10.1103/physrevlett.91.187903] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2002] [Revised: 07/21/2003] [Indexed: 05/24/2023]
Abstract
For a practical quantum computer to operate, it is essential to properly manage decoherence. One important technique for doing this is the use of "decoherence-free subspaces" (DFSs), which have recently been demonstrated. Here we present the first use of DFSs to improve the performance of a quantum algorithm. An optical implementation of the Deutsch-Jozsa algorithm can be made insensitive to a particular class of phase noise by encoding information in the appropriate subspaces; we observe a reduction of the error rate from 35% to 7%, essentially its value in the absence of noise.
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Affiliation(s)
- M Mohseni
- Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, Canada, M5S 1A7
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Pittman TB, Franson JD. Violation of Bell's inequality with photons from independent sources. PHYSICAL REVIEW LETTERS 2003; 90:240401. [PMID: 12857180 DOI: 10.1103/physrevlett.90.240401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2003] [Indexed: 05/24/2023]
Abstract
We report a violation of Bell's inequality using one photon from a parametric down-conversion source and a second photon from an attenuated laser beam. The two photons were entangled at a beam splitter using the postselection technique of Shih and Alley [Phys. Rev. Lett. 61, 2921 (1988)]]. A quantum interference pattern with a visibility of 91% was obtained using the photons from these independent sources, as compared with a visibility of 99.4% using two photons from a central parametric down-conversion source.
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Affiliation(s)
- T B Pittman
- Johns Hopkins University, Applied Physics Laboratory, Laurel, Maryland 20723, USA
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Owschimikow N, Gmachl C, Belyanin A, Kocharovsky V, Sivco DL, Colombelli R, Capasso F, Cho AY. Resonant second-order nonlinear optical processes in quantum cascade lasers. PHYSICAL REVIEW LETTERS 2003; 90:043902. [PMID: 12570424 DOI: 10.1103/physrevlett.90.043902] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2002] [Indexed: 05/24/2023]
Abstract
We demonstrate an efficient intracavity nonlinear interaction of laser modes in a specially adapted quantum cascade laser. A two-wavelength quantum cascade laser structure emitting at wavelengths of 7.1 and 9.5 micrometer included cascaded resonant optical intersubband transitions in an intracavity configuration leading to resonantly enhanced sum-frequency and second-harmonic generation at wavelengths of 4.1, 3.6, and 4.7 micrometer respectively. Laser peak optical powers of 60 and 80 mW resulted in 30 nW of sum-frequency signal and 10-15 nW of second-harmonic signal, both in good agreement with theoretical calculations.
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Affiliation(s)
- Nina Owschimikow
- Bell Laboratories, Lucent Technologies, 600 Mountain Avenue, Murray Hill, New Jersey 07974, USA
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Resch KJ, Lundeen JS, Steinberg AM. Conditional-phase switch at the single-photon level. PHYSICAL REVIEW LETTERS 2002; 89:037904. [PMID: 12144421 DOI: 10.1103/physrevlett.89.037904] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2002] [Indexed: 05/23/2023]
Abstract
We present an experimental realization of a two-photon conditional phase switch, related to the " c-phis;" gate of quantum computation. This gate relies on quantum interference between photon pairs and generates entanglement between two optical modes through the process of spontaneous parametric down-conversion (SPDC). The interference effect serves to enhance the effective nonlinearity by many orders of magnitude, so it is significant at the quantum (single-photon) level. By adjusting the relative optical phase between the classical pump for SPDC and the pair of input modes, one can impress a large phase shift on one beam which depends on the presence or absence of a single photon in a control mode.
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Affiliation(s)
- Kevin J Resch
- Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, Canada M5S 1A7
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Resch KJ, Lundeen JS, Steinberg AM. Quantum state preparation and conditional coherence. PHYSICAL REVIEW LETTERS 2002; 88:113601. [PMID: 11909400 DOI: 10.1103/physrevlett.88.113601] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2001] [Indexed: 05/23/2023]
Abstract
It is well known that spontaneous parametric down-conversion can be used to probabilistically prepare single-photon states. We have performed an experiment in which arbitrary superpositions of zero- and one-photon states can be prepared by appropriate postselection. The optical phase, which is meaningful only for superpositions of photon number, is related to the relative phase between the zero- and one-photon states. Whereas the light from spontaneous parametric down-conversion has an undefined phase, we show that this technique collapses one beam to a state of well-defined optical phase when a measurement succeeds on the other beam.
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Affiliation(s)
- K J Resch
- Department of Physics, University of Toronto, 60 St. George Street, Toronto ON M5S 1A7, Canada
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