Storage and retrieval of nonclassical photon pairs and conditional single photons generated by parametric down-conversion process

TL;DR

This paper demonstrates the storage and retrieval of broadband parametric down-conversion photons using electromagnetically induced transparency, confirming their nonclassical nature and enabling conditional single photon generation.

Contribution

It introduces a method to store broadband PDC photons within the EIT window and verifies their nonclassical properties after retrieval, advancing quantum memory techniques.

Findings

Successfully stored and retrieved PDC photons within the EIT bandwidth.

Confirmed nonclassicality of retrieved photons via photon counting.

Demonstrated conditional single photon storage with non-classical properties.

Abstract

Storage and retrieval of parametric down-conversion (PDC) photons are demonstrated with electromagnetically induced transparency (EIT). Extreme frequency filtering is performed for THz order of broadband PDC light and the frequency bandwidth of the light is reduced to MHz order. Storage and retrieval procedures are carried out for the frequency filtered PDC photons. Since the filtered bandwidth [full width at half-maximum (FWHM) = 9 MHz] is within the EIT window (FWHM = 12.6 MHz), the flux of the PDC light is successfully stored and retrieved. The nonclassicality of the retrieved light is confirmed by using photon counting method, where the classical inequality which is only satisfied for classical light fields is introduced. Since the PDC photons can be utilized for producing the single photon state conditionally, storage and retrieval procedures are also performed for the conditional single photons. Anti-correlation parameter used for checking the property of single photon state shows the value less than 1, which means the retrieved light is in a non-classical region.