Abstract
Manipulating polarization entanglement of paired photons is always of great interest for understanding the quantum nature of photons and exploring their applications in quantum information processing and quantum communication. Narrowband biphotons with polarization entanglement are especially important for a quantum network based on efficient photon–atom interactions. In most demonstrated cases, the polarization-entangled states are manipulated through the birefringent effect. In this Letter, we produce narrowband polarization-entangled biphotons from spontaneous four-wave mixing in cold atoms and demonstrate a new method to tune the phase of the polarization entanglement by varying the frequency of one of the classical driving lasers. This is achieved through two-photon interference with a path-exchange symmetry. Our result represents a precision control of polarization entanglement from the frequency domain, and may have promising applications in quantum information and precision measurement.
Highlights
Entanglement, one of most delicate natures of quantum systems, plays a central role in quantum communication and quantum computation [1,2]
Using two identical nonlinear crystals placed with the optical axes orthogonal to each other, Kwiat et al showed that the relative phase can be directly tuned with the polarization of the pump laser [12]
In this Letter, we demonstrate the generation of polarizationentangled narrowband biphotons from spontaneous four-wave mixing (SFWM) in cold atoms with tunable phase by varying the frequency of the pump laser
Summary
Entanglement, one of most delicate natures of quantum systems, plays a central role in quantum communication and quantum computation [1,2]. In this Letter, we demonstrate the generation of polarizationentangled narrowband biphotons from SFWM in cold atoms with tunable phase by varying the frequency of the pump laser. Using a scheme of two-photon interference with path-exchange symmetry, we obtain polarization entanglement for narrowband biphotons.
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