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arXiv:1408.6407 · Physical Review A

Low-noise macroscopic twin beams

T. Sh. Iskhakov, Vladyslav C. Usenko, Radim Filip, Maria V. Chekhova, Gerd Leuchs

Published Apr 26, 2016• 25 citations
arXivHTMLPDF

Abstract

Applying a multiphoton-subtraction technique to the two-color macroscopic squeezed vacuum state of light generated via high-gain parametric down-conversion we conditionally prepare a different state of light: bright multimode low-noise twin beams. A lower noise in the sum of the photon numbers opens a possibility to encode information into this variable while keeping the nonclassical character of the state. The obtained results demonstrate up to eightfold suppression of noise in each beam while preserving and even moderately improving the nonclassical photon-number correlations between the beams. The prepared low-noise macroscopic state, containing up to 2000 photons per mode, is not among the Gaussian states achievable through nonlinear optical processes. Apart from that, we suggest a method for measuring quantum efficiency, which is based on the Fano factor measurement. The proposed technique substantially improves the usefulness of twin beams for quantum communication and metrology.

DOI
10.1103/physreva.93.043849

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Applying a multiphoton-subtraction technique to the two-color macroscopic squeezed vacuum state of light generated via high-gain parametric down-conversion we conditionally prepare a different state of light: bright multimode low-noise twin beams. A lower noise in the sum of the photon numbers opens a possibility to encode information into this variable while keeping the nonclassical character of the state. The obtained results demonstrate up to eightfold suppression of noise in each beam while preserving and even moderately improving the nonclassical photon-number correlations between the beams. The prepared low-noise macroscopic state, containing up to 2000 photons per mode, is not among the Gaussian states achievable through nonlinear optical processes. Apart from that, we suggest a method for measuring quantum efficiency, which is based on the Fano factor measurement. The proposed technique substantially improves the usefulness of twin beams for quantum communication and metrology.
We demonstrate sub-shot-noise photon-number correlations in a (temporal) multimode mesoscopic ($\ensuremath{\sim}{10}^{3}$ detected photons) twin beam produced by picosecond-pulsed spontaneous nondegenerate parametric down-conversion. We have separately detected the signal and idler distributions of photons collected in twin coherence areas and found that the variance of the photon-count difference goes below the shot-noise limit by 3.25dB3.25\phantom{\rule{0.3em}{0ex}}\mathrm{dB}3.25dB. The number of temporal modes contained in the twin beam, as well as the size of the twin coherence areas, depends on the pump intensity. Our scheme is based on spontaneous down-conversion and thus does not suffer from limitations due to the finite gain of the parametric process. Twin beams are also used to demonstrate the conditional preparation of a nonclassical (sub-Poissonian) state.
States obtained from multimode twin beams by symmetric as well as asymmetric photon subtraction are experimentally investigated. Using the joint photocount distributions measured by an intensified CCD camera, their joint photon-number distributions are reconstructed. Mean photon numbers, Fano factors, and noise-reduction parameters are determined for the group of states reached by subtracting up to four photocounts in each beam. Photon subtraction is monitored using the nonclassicality depths and joint quasidistributions of integrated intensities of the emerging states. The non-Gaussianity of the obtained states is also determined. The states reached by coherent photon subtraction are also analyzed. The investigations represent an important step towards the use of photon-subtracted twin beams in sub-shot-noise metrology and imaging. Published by the American Physical Society 2024
The robustness of nonclassical correlations exhibited by mesoscopic twin-beam states of light makes them useful for applications in the context of quantum technologies, such as for underwater quantum communication. To this aim, it is crucial to optimize the production of such quantum states of light, and study their level of nonclassicality in terms of different nonclassicality criteria. In this work, we realize an efficient source of well-populated twin-beam states in the red spectral region by pumping parametric down conversion with a natively sub-picosecond laser system. The nonclassical character of such states is investigated in terms of both the noise reduction factor and high-order correlation functions. The obtained results encourage the exploitation of this source in further optical schemes for practical applications.
Two-beam states obtained by partial photon-number-resolving detection in one beam of a multi-mode twin beam are experimentally investigated using an intensified CCD camera. In these states, sub-Poissonian photon-number distributions in one beam are accompanied by sub-shot-noise fluctuations in the photon-number difference of both beams. Multi-mode character of the twin beam implying the beam nearly Poissonian statistics is critical for reaching sub-Poissonian photon-number distributions, which contrasts with the use of a two-mode squeezed vacuum state. Relative intensities of both nonclassical effects as they depend on the generation conditions are investigated both theoretically and experimentally using photon-number distributions of these fields. Fano factor, noise-reduction parameter, local and global nonclassicality depths, degree of photon-number coherence, mutual entropy as a non-Gaussianity quantifier, and negative quasi-distributions of integrated intensities are used to characterize these fields. Spatial photon-pair correlations as means for improving the field properties are employed. These states are appealing for quantum metrology and imaging including the virtual-state entangled-photon spectroscopy.
Using the method of photon addition into both beams of a multi-mode twin beam, a new kind of highly nonclassical states is obtained. As these states exhibit tight photon-number cross-correlations and are endowed with marginal sub-Poissonian photon-number distributions, we suggest to call them sub-Poissonian twin beams. We reveal their properties in the model as well as experimentally using mesoscopic twin beams. An intensified CCD camera as a photon-number resolving detector is applied to prepare as well as characterize the states with up to three photons added into each beam and containing from 2.8 to 7.5 photons in average in each beam. Their nonclassicality as well as non-Gaussianity are determined to demonstrate their prominent features. Spatial correlations of photons in the beams are exploited to improve the properties of the generated states. The beams are promising as the quantum light source for virtual-state entangled-photon spectroscopy. Their properties are prospective for monitoring and manipulating two-photon light–matter interactions.
Squeezed vacuum with large photon numbers is an example of a macroscopic system with nonclassical properties. These properties are manifested in pairwise intensity correlations, also called twin-beam squeezing. We produce squeezed vacuum in a traveling-wave pulse-pumped frequency non-degenerate optical parametric amplifier (NOPA). Twin-beam squeezing is measured via direct detection and measurement of the difference-signal variance for two balanced detectors. It is shown that the study of the intensity correlations using this method requires a collection of a large number of modes, both longitudinal and transverse.