Two polarization-entangled sources from the same semiconductor chip

Abstract

Generating nonclassical states of photons such as polarization-entangled states on a monolithic chip is a crucial step towards practical applications of optical quantum information processing such as quantum computing and quantum key distribution. Here we demonstrate two polarization-entangled photon sources in a single monolithic semiconductor waveguide. The first source is achieved through the concurrent utilization of two spontaneous parametric down-conversion (SPDC) processes, namely, type-0 and type-I SPDC processes. The chip can also generate polarization-entangled photons via the type-II SPDC process, enabling the generation of both copolarized-and cross-polarized polarization-entangled photons in the same device. In both cases, polarization entanglement is generated directly on the chip without the use of any off-chip compensation, interferometry, or bandpass filtering. This enables direct, chip-based generation of both Bell states (|H,H + |V ,V )/ √ 2 and (|H,V + |V ,H )/ √ 2 simultaneously utilizing the same pump source. In addition, based on compound semiconductors, this chip can be directly integrated with it own pump laser. This technique ushers an era of self-contained, integrated, electrically pumped, room-temperature polarization-entangled photon sources.

Generation and manipulation of entangled photons on silicon chips

“…Lv et al [61] generated polarization entanglement by means of the birefringence of a single SWW. Various polarization entanglement sources based on an χ (2) nonlinear waveguide made of (Al)GaAs have also been demonstrated [62][63][64][65][66]; these experiments employing the direct band-gap materials paved the way to the realization of a polarization entanglement source driven by current injection [67,68]. These results show important steps toward the realization of an integrated quantum information system using the polarizations of light.…”

Monolithic semiconductor chips as a source for broadband wavelength-multiplexed polarization entangled photons

“…For practical applications, compact, robust sources of entangled photons capable of integrating with other components in the system should be developed. Recent developments in integrated quantum photonics have achieved compact generation of entangled photons in monolithic waveguide devices using SPDC [15][16][17] or spontaneous four-wave mixing (SFWM) [18][19][20]. However, the demonstration of broadband wavelength-multiplexed entangled photons based on a single waveguide chip has not been reported.…”

Temporally versatile polarization entanglement from Bragg reflection waveguides

“…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.…”

“…For the creation of polarization entanglement we employ the scheme illustrated in Fig. 1(a), also used for BRWs in Refs [14,20] without delay compensation. The state from (1) is split at a dichroic mirror, which we model as a frequency dependent beam splitter.…”

“…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].…”