Generation of maximally-polarization-entangled photons on a chip

Zhukovsky, Sergei V.; Helt, L. G.; Kang, Dongpeng; Abolghasem, Payam; Helmy, Amr S.; Sipe, J. E.

doi:10.1103/physreva.85.013838

Cited by 35 publications

(45 citation statements)

References 34 publications

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“…The traditional method to produce indistinguishable single photons is heralding time-frequency entangled biphotons generated from spontaneous parametric down-conversion (SPDC) in a nonlinear crystal which is pumped by ultrashort pulses [4,5,8]. In recent decades many new physical systems have been developed [9-13] to obtain pure single photons without time-frequency entanglement built in.In the community of quantum communication, SPDC in χ ð2Þ nonlinear media is still the preferable way to produce entangled biphotons because of its simplicity in the operation and the potential for on-chip integration and scaling up [14][15][16]. However, the intrinsic feasible phase matching condition of SPDC crystal allows an extremely broad range of temporal modes.…”

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confidence: 99%

“…In the community of quantum communication, SPDC in χ ð2Þ nonlinear media is still the preferable way to produce entangled biphotons because of its simplicity in the operation and the potential for on-chip integration and scaling up [14][15][16]. However, the intrinsic feasible phase matching condition of SPDC crystal allows an extremely broad range of temporal modes.…”

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confidence: 99%

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Temporal Purity and Quantum Interference of Single Photons from Two Independent Cold Atomic Ensembles

Qian

Cao

et al. 2016

Phys. Rev. Lett.

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The temporal purity of single photons is crucial to the indistinguishability of independent photon sources for the fundamental study of the quantum nature of light and the development of photonic technologies. Currently, the technique for single photons heralded from time-frequency entangled biphotons created in nonlinear crystals does not guarantee the temporal-quantum purity, except using spectral filtering. Nevertheless, an entirely different situation is anticipated for narrow-band biphotons with a coherence time far longer than the time resolution of a single-photon detector. Here we demonstrate temporally pure single photons with a coherence time of 100 ns, directly heralded from the time-frequency entangled biphotons generated by spontaneous four-wave mixing in cold atomic ensembles, without any supplemented filters or cavities. A near-perfect purity and indistinguishability are both verified through Hong-Ou-Mandel quantum interference using single photons from two independent cold atomic ensembles. The time-frequency entanglement provides a route to manipulate the pure temporal state of the single-photon source. DOI: 10.1103/PhysRevLett.117.013602 The purity of the quantum state of a single photon is a prerequisite of its indistinguishability with single photons from other independent sources, and the latter is an essential basis for the realization of a scalable quantum network with distant and independent nodes [1][2][3][4][5]. Furthermore, the temporal purity of a single photon is crucial to the development of photonic technologies for quantum information science [6,7]. The traditional method to produce indistinguishable single photons is heralding time-frequency entangled biphotons generated from spontaneous parametric down-conversion (SPDC) in a nonlinear crystal which is pumped by ultrashort pulses [4,5,8]. In recent decades many new physical systems have been developed [9-13] to obtain pure single photons without time-frequency entanglement built in.In the community of quantum communication, SPDC in χ ð2Þ nonlinear media is still the preferable way to produce entangled biphotons because of its simplicity in the operation and the potential for on-chip integration and scaling up [14][15][16]. However, the intrinsic feasible phase matching condition of SPDC crystal allows an extremely broad range of temporal modes. Therefore, the typical temporal coherence time of the photon source is of femtosecond scale. Compared to the time response of most commercial single-photon detectors, which is about 1 ns, this temporal coherence time is so short that the trigger photon of the heralded single photon is measured with a large time uncertainty. This time uncertainty damages the temporal quantum purity of the single-photon source. To circumvent the time uncertainty problem due to the slowness of the detectors, a common practice is to use external spectral filtering including passive filtering with narrowband filters [4,5,17] and active filtering with an optical cavity [18]. In this case, the temporal state o...

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confidence: 99%

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confidence: 99%

Temporal Purity and Quantum Interference of Single Photons from Two Independent Cold Atomic Ensembles

Qian

Cao

et al. 2016

Phys. Rev. Lett.

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“…Moreover, the purity of the state in (7) is greatly dependent on the temporal characteristics of the D-parameter that are governed by the properties of the underlying PDC process [33][34][35]. In our experiment shown in Fig.…”

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confidence: 76%

“…The complex-valued off-diagonal elements, D(τ ) and its complex conjugate D * (τ ), quantify the amount of entanglement in the created state, which we call the degree of polarization entanglement, shortly D-parameter [33]. This parameter is highly dependent on τ and the state characteristics can be manipulated by changing the relative delay between signal and idler.…”

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confidence: 99%

Temporally versatile polarization entanglement from Bragg reflection waveguides

et al. 2017

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Bragg-reflection waveguides emitting broadband parametric down-conversion (PDC) have been proven to be well suited for the on-chip generation of polarization entanglement in a straightforward fashion [R. T. Horn et al., Sci. Rep. 3, 2314]. Here, we investigate how the properties of the created states can be modified by controlling the relative temporal delay between the pair of photons created via PDC. Our results offer an easily accessible approach for changing the coherence of the polarization entanglement, in other words, to tune the phase of the off-diagonal elements of the density matrix. Furthermore, we provide valuable insight in the engineering of these states directly at the source.The verification of the non-classical nature of quantum objects, such as photons, plays an important role to ensure a successful implementation of forthcoming quantum technologies. Among theses tasks is the preparation and characterization of polarization entanglement that provides some of the strongest evidence of the quantum features of light [1][2][3]. Since the first realizations with parametric down-conversion (PDC) in bulk crystals more than two decades ago [4][5][6], a lot of effort has been put in replacing them both with ferroelectric [7][8][9][10][11] and semiconductor waveguides [12][13][14], which provide higher brightnesses and easier alignment in collinear configurations.In one of such configurations, the cross-polarized PDC photon pairs-called signal and idler-that have at least some nanometers of spectral extent, are divided on a dichroic beam splitter into two paths [15][16][17][18][19]. Due to a strict frequency or energy correlation between signal and idler, a two-partite polarization superposition is created between the output paths of the dichroic mirror. Often, a continuous-wave pump laser is utilized to guarantee tight correlations in the spectral domain [14,20].Bragg-reflection waveguides (BRWs) made of AlGaAs generate indistinguishable photon pairs over several tens of nanometers [14,21] and they have been utilized for narrowband multiplexing of polarization entanglement [22,23]. Due to the very small birefringence between the orthogonally-polarized signal and idler [24], BRWs may work reasonably well in this configuration even without compensating their temporal walk-off. However, their group index difference is large enough to result into an uncompensated phase. Therefore, the engineering of the spectro-temporal degree of freedom of PDC photon pairs from BRWs is essential for the controlled creation and manipulation of the polarization entanglement.Changes in the coherence of the polarization entangled states, that is their phase, provide an interesting degree of freedom for the state manipulation [2]. When regarding PDC sources, this is usually accomplished by * kaisa.laiho@uibk.ac.at modifying the characteristics of one of the entangled parties with birefringent retarders [14,25,26]. However, the phase control over the joint state can possibly be realized more easily [27][28][29]. Here, we generat...

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“…As well as being both compact and efficient, integrated photon pair sources have also shown unprecedented versatility in tailoring the properties of the generated twin-photon state through dispersion engineering and birefringence management, thereby establishing control over the spectral and polarization entanglement [15][16][17], photon bandwidths [18], and degree of non-degeneracy. A single device can be designed to produce a variety of quantum states.…”

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confidence: 99%

Deterministic separation of arbitrary photon pair states in integrated quantum circuits

Marchildon

Helmy

2016

Laser & Photonics Reviews

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Entangled photon pairs generated within integrated devices must often be spatially separated for their subsequent manipulation in quantum circuits. Separation that is both deterministic and universal can in principle be achieved through anticoalescent two-photon quantum interference. However, such interference-facilitated pair separation (IFPS) has not been extensively studied in the integrated setting, where the strong polarization and wavelength dependencies of integrated couplers -as opposed to bulk-optics beamsplitters -can have important implications for performance beyond the identical-photon regime. This paper provides a detailed review of IFPS and examines how these dependencies impact separation fidelity and interference visibility. Focus is given to IFPS mediated by an integrated directional coupler. The analysis applies equally to both on-chip and in-fiber implementations, and can be expanded to other coupler architectures such as multimode interferometers. When coupler dispersion is present, the separation performance can depend on photon bandwidth, spectral entanglement, and the linearity of the dispersion. Under appropriate conditions, reduction in the separation fidelity due to loss of non-classical interference can be perfectly compensated for by classical wavelength demultiplexing effects. This work informs the design as well as the performance assessment of circuits for achieving universal photon pair separation for states with tunable arbitrary properties.

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Generation of maximally-polarization-entangled photons on a chip

Cited by 35 publications

References 34 publications

Temporal Purity and Quantum Interference of Single Photons from Two Independent Cold Atomic Ensembles

Temporal Purity and Quantum Interference of Single Photons from Two Independent Cold Atomic Ensembles

Temporally versatile polarization entanglement from Bragg reflection waveguides

Deterministic separation of arbitrary photon pair states in integrated quantum circuits

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