Spectral polarization and spectral phase control of time-energy entangled photons

Abstract

We demonstrate a scheme to spectrally manipulate a collinear, continuous stream of time and energy entangled photons to generate beamlike, bandwidth-limited fluxes of polarization-entangled photons with nearly degenerate wavelengths. Utilizing an ultrashort-pulse shaper to control the spectral phase and polarization of the photon pairs, we tailor the shape of the Hong-Ou-Mandel interference pattern, demonstrating the rules that govern the dependence of this interference pattern on the spectral phases of the photons. We then use the pulse shaper to generate all four polarization Bell states. The singlet state generated by this scheme forms a very robust decoherence-free subspace, extremely suitable for long-distance fiber-optics-based quantum communication. DOI: 10.1103/PhysRevA.75.043804 PACS number͑s͒: 42.50.Dv, 03.67.Mn, 42.65.Lm, 42.65.Re Parametrically generated polarization-entangled photons are a primary resource in the fields of quantum communication and quantum information ͓1͔, motivating an ongoing search for better means for the generation and control of high fluxes of such photons ͓2-4͔. In particular, the generation of the singlet Bell state has raised a considerable interest due to the fact that it forms a decoherence-free subspace ͑DFS͒, which is inherently immune to collective decoherence ͓5,6͔. The upper limit for the flux of entangled photon pairs is typically set by the spatial divergence of the down-converted photons, or by the repetition rate of the pump pulses, in the case of pulsed down-conversion. In both cases, the achievable flux is many orders of magnitude lower than the physical upper limit, which is set by the down-converted bandwidth ͓7,8͔. Although collinear and continuous downconversion enables efficient generation and collection of photon pairs, resulting in ultrahigh ͑bandwidth-limited͒ fluxes as high as 10 12 s −1 ͓8͔, such a single-mode configuration does not readily enable polarization entanglement.Pulse-shaping techniques were recently introduced as a means to control the spectral properties of broadband downconverted photons ͓9͔. In this work we use a phase and polarization pulse shaper ͓10͔ to control both the phase and the polarization of each of the spectral modes of copropagating entangled photons. Our precise control of the phase and polarization in the frequency domain is demonstrated by tailoring the shape of the Hong-Ou-Mandel interference pattern ͓11͔. Exploiting the fact that the photon pairs are hyperentangled, i.e., entangled in more than one degree of freedom ͓12͔, we treat the frequency domain as a two-dimensional subspace and thus use the pulse shaper as a Bell-state synthesizer, generating all four polarization Bell states in a collinear, beamlike fashion, which enables bandwidth-limited fluxes, and is suitable for fiber-optic-based quantum communication. The fact that in this scheme the photons of each pair share the same single spatial mode and are nearly degenerate makes it a very robust and practical DFS. Specifically, if the photons travel through th...

Bloch Oscillations of Path-Entangled Photons

“…The ratio of the detection probabilities for the N00N and mixed states is given by (1,1) = 0, the photons are bunched and are never found in the two different branches of the BO; scanning the delay between the input ports of the lattice will yield a HOM dip. When γ (1,1) = 2, the photons are antibunched, and a delay scan will result in a HOM peak [21]. We next study input states which exhibit correlation oscillations with shorter periods.…”

Biphoton Pulse Shaping

“…13.4a is unable to resolve biphoton correlations on the few-and sub-picosecond time scales. And although there are several interesting examples of shaping experiments with such slow detectors [30][31][32], the full potential of programmable pulse shaping is only realized on the ultrafast time scale. This timing resolution problem permeates classical optics as well, where correlation techniques based on nonlinear optical interactions have facilitated high-resolution temporal measurements of ultrashort pulses [14].…”

Coherence and dimensionality of intense spatiospectral twin beams

“…As a consequence, the developed theoretical models usually invoke the quasi-monochromatic approximation. When combined with the pump-field quasi-plane-wave approximation, a twin beam in the model has been decomposed into many more-less independent pairs of signal and idler modes localized both in the spectrum and transverse wave-vector plane [18][19][20][21]. The dynamics of individual pairs of modes has then been treated by the solution of linear Heisenberg equations.…”