Chip-to-chip quantum photonic interconnect by path-polarization interconversion

Abstract

Integrated photonics has enabled much progress towards quantum technologies. Many applications, e.g., quantum communication, sensing, and distributed cloud quantum computing, require coherent photonic interconnection between separate on--chip subsystems. Large--scale quantum computing architectures and systems may ultimately require quantum interconnects to enable scaling beyond the limits of a single wafer, and towards multi--chip systems. However, coherently connecting separate chips remains a challenge, due to the fragility of entangled quantum states. The distribution and manipulation of entanglement between multiple integrated devices is one of the strictest requirements of these systems. Here, we report the first quantum photonic interconnect, demonstrating high--fidelity entanglement distribution and manipulation between two separate photonic chips, implemented using state--of--the--art silicon photonics. Path--entangled states are generated on one chip, and distributed to another chip by interconverting between path and polarization degrees of freedom, via a two--dimensional grating coupler on each chip. This path--to--polarization conversion allows entangled quantum states to be coherently distributed. We use integrated state analyzers to confirm a Bell--type violation of S=2.638±0.039 between the two chips. With further improvements in loss, this quantum photonic interconnect will provide new levels of flexibility in quantum systems and architectures.

Multidimensional quantum entanglement with large-scale integrated optics

“…Entangled path-encoded qubits can be generated by coherently pumping two spontaneous parametric down conversion (28,29) or spontaneous four-wave mixing (SFWM) photon-pair sources (30,31). The approach can be generalized to qudits via the generation of photons entangled over d spatial modes by coherently pumping d sources (28,32).…”

Resonance energy transfer and quantum entanglement mediated by epsilon-near-zero and other plasmonic waveguide systems

“…It is also demonstrated that the introduction of active (gain) media inside the plasmonic ENZ nanochannels can lead to perfect loss compensation of the inherent 28 (nonradiative) plasmonic losses that, subsequently, reduces decoherence and further boosts transient quantum entanglement. We envision that the presented passive and active ENZ mediated RET and entangled states will find applications in future quantum information and communications integrated systems on a chip [58,59], the design of new low-threshold subwavelength nanolasers [60], and the creation of ultrasensitive quantum metrology devices [61]. Hence, effective ENZ waveguide media have the potential to become crucial components to the emerging field of quantum plasmonics [9].…”

Hybrid waveguide scheme for silicon-based quantum photonic circuits with quantum light sources

“…The photon pairs are finally sent to the part of quantum state analyzer to measure the property of path entanglement. The analyzer consists of two balanced MZIs, which can realize the  z R and  y R rotations on the signal/idler photons [23,29]. At the outputs of the MZIs, four grating couplers are used to couple the photons to optical fibers.…”