Generation and Direct Detection of Broadband Mesoscopic Polarization-Squeezed Vacuum

Iskhakov, T. Sh.; Chekhova, Maria V.; Leuchs, Gerd

doi:10.1103/physrevlett.102.183602

Cited by 114 publications

(100 citation statements)

References 42 publications

(35 reference statements)

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“…They are produced by optimal phase-covariant quantum cloning via phase-sensitive parametric amplification [2,22,23] of single photons of a defined polarization (ϕ or ϕ ⊥ , respectively):…”

Section: Filtering Of "Macroscopic" Qubitsmentioning

confidence: 99%

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Filtering of the absolute value of photon-number difference for two-mode macroscopic quantum superpositions

et al. 2012

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We discuss a device capable of filtering out two-mode states of light with mode populations differing by more than a certain threshold, while not revealing which mode is more populated. It would allow engineering of macroscopic quantum states of light in a way which is preserving specific superpositions. As a result, it would enhance optical phase estimation with these states as well as distinguishability of "macroscopic" qubits. We propose an optical scheme, which is a relatively simple, albeit nonideal, operational implementation of such a filter. It uses tapping of the original polarization two-mode field, with a polarization-neutral beam splitter of low reflectivity. Next, the reflected beams are suitably interfered on a polarizing beam splitter. It is oriented such that it selects unbiased polarization modes with respect to the original ones. The more an incoming two-mode Fock state is unequally populated, the more the polarizing beam-splitter output modes are equally populated. This effect is especially pronounced for highly populated states. Additionally, for such states we expect strong population correlations between the original fields and the tapped one. Thus, after a photon-number measurement of the polarizing beam-splitter outputs, a feed-forward loop can be used to let through a shutter the field, which was transmitted by the tapping beam splitter. This happens only if the counts at the outputs are roughly equal. In such a case, the transmitted field differs strongly in occupation number of the two modes, while information on which mode is more populated is nonexistent (a necessary condition for preserving superpositions).

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Section: Filtering Of "Macroscopic" Qubitsmentioning

confidence: 99%

“…However, in the high-photon-number regime, the detectors are not single photon resolving, but distinguish counts varying by at least ±150 photons [23]. Thus, macroqubits are hardly distinguishable with direct detection [22].…”

Section: Filtering Of "Macroscopic" Qubitsmentioning

confidence: 99%

Filtering of the absolute value of photon-number difference for two-mode macroscopic quantum superpositions

et al. 2012

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“…Many works, performed in the single-photon regime, have highlighted the correlations and coherence properties of photon pairs either in spectrum or space [2][3][4][5][6][7][8][9]. In the past ten years, also high-gain PDC, leading to a large number of photons per mode, has been the object of several studies for its interesting properties of subshot-noise spatial intensity correlations [10][11][12][13] and macroscopic entanglement [14][15][16][17][18][19]. More recently, the spectral features of macroscopic twin-beam states have been investigated in the collinear interaction geometry close to frequency degeneracy [20].…”

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confidence: 99%

Coherence properties of high-gain twin beams

et al. 2014

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Twin-beam coherence properties are analyzed both in the spatial and spectral domains at high-gain regime including pump depletion. The increase of the size of intensity auto-and cross-correlation areas at increasing pump power is replaced by a decrease in the pump depletion regime. This effect is interpreted as a progressive loss in the mode selection occurring at high-gain amplification. The experimental determination of the number of spatio-spectral modes from g (2) -function measurements confirms this explanation. The process of parametric down-conversion (PDC) in bulk nonlinear crystals generates twin-beam states of light that are naturally multi-mode both in spectrum and space [1]. Many works, performed in the single-photon regime, have highlighted the correlations and coherence properties of photon pairs either in spectrum or space [2][3][4][5][6][7][8][9]. In the past ten years, also high-gain PDC, leading to a large number of photons per mode, has been the object of several studies for its interesting properties of subshot-noise spatial intensity correlations [10][11][12][13] and macroscopic entanglement [14][15][16][17][18][19]. More recently, the spectral features of macroscopic twin-beam states have been investigated in the collinear interaction geometry close to frequency degeneracy [20]. Moreover, in the high-gain regime, the X-shaped coherence of the PDC output field [21] and the X-shaped spatio-temporal twin beam near-field correlations [22][23][24], originating from the space-time coupling in the phase-matching, have been demonstrated. The high-gain PDC process is also in the focus of attention for its potential applications. For instance, high-gain PDC has been used for quantum imaging [25], ghost imaging [26], and absolute calibration of photo-detectors [27,28]. The possibility to involve such bright states in interactions with material quantum objects (atoms, molecules, quantum dots) has been also addressed. Also the application of twin beams to quantum memories has been recently suggested [29].In this paper, we present a joint investigation of spatial and spectral features of twin-beam states produced in the high-gain regime with non-negligible pump depletion. The coherence properties at different values of pump mean power are inferred by evaluating the intensity auto-and cross-correlation functions on single-shot images of the far-field (θ, λ) speckle-like pattern of the PDC radiation. The initial increase with PDC gain of the size of coherence areas, both in spectrum and space, gradually stops and, at a certain pump power, is replaced by a decrease. This behavior is due to the occurrence of a progressive pump depletion, which is testified by the evolution of the spatial and spectral pump beam profiles. A possible explanation can be given in terms of the varying population of Schmidt paired modes [30] that 'diagonalize' the nonlinear interaction. The number of effectively populated modes is experimentally accessed by the measurement of spatio-spectral intensity g (2) -correlation function. T...

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“…(1) are orthogonal, but in the high-photon-number regime, detection is not single-photon resolving [3] and they reveal effective overlap. This is an important issue for Bell-inequality violation and preselection can solve it.…”

Section: Macroscopic Entangled Statesmentioning

confidence: 99%

Bell-inequality tests with macroscopic entangled states of light

et al. 2011

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Quantum correlations may violate the Bell inequalities. Most experimental schemes confirming this prediction have been realized in all-optical Bell tests suffering from the detection loophole. Experiments which simultaneously close this loophole and the locality loophole are highly desirable and remain challenging. An approach to loophole-free Bell tests is based on amplification of the entangled photons (i.e., on macroscopic entanglement), for which an optical signal should be easy to detect. However, the macroscopic states are partially indistinguishable by classical detectors. An interesting idea to overcome these limitations is to replace the postselection by an appropriate preselection immediately after the amplification. This is in the spirit of state preprocessing revealing hidden nonlocality. Here, we examine one of the possible preselections, but the presented tools can be used for analysis of other schemes. Filtering methods making the macroscopic entanglement useful for Bell tests and quantum protocols are the subject of an intensive study in the field nowadays.

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Generation and Direct Detection of Broadband Mesoscopic Polarization-Squeezed Vacuum

Cited by 114 publications

References 42 publications

Filtering of the absolute value of photon-number difference for two-mode macroscopic quantum superpositions

Filtering of the absolute value of photon-number difference for two-mode macroscopic quantum superpositions

Coherence properties of high-gain twin beams

Bell-inequality tests with macroscopic entangled states of light

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