On-demand photonic entanglement synthesizer

Abstract

Quantum information protocols require various types of entanglement, such as Einstein-Podolsky-Rosen, Greenberger-Horne-Zeilinger, and cluster states. In optics, on-demand preparation of these states has been realized by squeezed light sources, but such experiments require different optical circuits for different entangled states, thus lacking versatility. Here, we demonstrate an on-demand entanglement synthesizer that programmably generates all these entangled states from a single squeezed light source. This is achieved by a loop-based circuit that is dynamically controllable at nanosecond time scales and processes optical pulses in the time domain. We verify the generation of five different small-scale entangled states and a large-scale cluster state containing more than 1000 modes without changing the optical circuit. Moreover, this circuit enables storage and release of one part of the generated entangled state, thus working as a quantum memory. Our demonstration should open a way for a more general entanglement synthesizer and a scalable quantum processor.

Toward large-scale fault-tolerant universal photonic quantum computing

“…Recently, part of the loop-based architecture in Fig. 8(a) was demonstrated experimentally 15 ; the setup contains one squeezed light source, a single optical loop, a variable beam splitter, a variable phase shifter, and a homodyne detector with tunable measurement basis, as shown in Fig. 8(b).…”

“…Recent experiments on CV teleportation-based gates have reported the bandwidth of up to 100 MHz 111 , and there the bandwidth is mainly limited by the bandwidth of homodyne detectors 112 and squeezed light sources 113 . In order to achieve high-fidelity operations in such systems, the bandwidth of pulses need to be sufficiently narrower than 100 MHz, and for this purpose the temporal width has been set to ∼ 50 ns in actual experiments 15,93,111 .…”

“…The length of optical delay lines is manly limited by transmission losses and stability (rather than the coherence length of light sources, which can be much longer 116 ). Previous experiments for time-domain multiplexed CV quantum information processing have used free-space optical delay lines or optical fiber delay lines of a few tens of meters 12,13,15,93 at the wavelength of 860 nm. For much longer delay lines with sufficient stability and low losses, optical fibers at telecommunication wavelength are the reasonable choice (even though kilometer-scale free-space optical delay lines are possible in principle 117 ).…”

“…These two schemes enable us to programmably perform arbitrarily largescale quantum computing without changing the configuration of optical circuits. Recent experiments based on these schemes 12,13,15 clearly show superior performance to conventional schemes in scaling up photonic quantum computing. These schemes also offer several unique advantages to photonic quantum computing.…”

“…This idea itself has already been used to efficiently increase the number of optical modes for quantum computation and communication. However, it has recently been discovered that the timedomain multiplexing is even more powerful when combined with specific quantum computing schemes; time-domain multiplexed one-way quantum computation 12,13 and a loop-based architecture for photonic quantum computing 14,15 . These two schemes enable us to programmably perform arbitrarily largescale quantum computing without changing the configuration of optical circuits.…”