Sequential generation of linear cluster states from a single photon emitter

Abstract

Light states composed of multiple entangled photons—such as cluster states—are essential for developing and scaling-up quantum computing networks. Photonic cluster states can be obtained from single-photon sources and entangling gates, but so far this has only been done with probabilistic sources constrained to intrinsically low efficiencies, and an increasing hardware overhead. Here, we report the resource-efficient generation of polarization-encoded, individually-addressable photons in linear cluster states occupying a single spatial mode. We employ a single entangling-gate in a fiber loop configuration to sequentially entangle an ever-growing stream of photons originating from the currently most efficient single-photon source technology—a semiconductor quantum dot. With this apparatus, we demonstrate the generation of linear cluster states up to four photons in a single-mode fiber. The reported architecture can be programmed for linear-cluster states of any number of photons, that are required for photonic one-way quantum computing schemes.

Artificial Coherent States of Light by Multiphoton Interference in a Single-Photon Stream

“…4, g ð2Þ ð0Þ would show a peak which is not the case here. The simple characterization method based only on two-photon correlations measurement presented here could also be useful for characterization of photonic cluster states demonstrated recently [16,17]. In order to determine how many photons are contributing to the quasicoherent states here, by comparing our experimental results to a photon-truncated theoretical model, we see that at least 3 photons are needed to explain our results.…”

“…1), where HOM interference happens at a half-wave plate in polarization space [12]. Similar setups are proposed for boson sampling [13,14] and used for producing linear photonic cluster states [15][16][17], an emerging resource for universal quantum computation [6,18,19]. Since we operate with a random but continuous single-photon stream, the repeated quantum interference and enlargement of the spatiotemporal superposition leads to an infinitely long quantum superposition.…”

“…A difference of the artificial coherent states here to conventional coherent light is that the photons of the artificial coherent state are correlated with others separated by multiples of the loop delay, this is typical for systems with time-delayed feedback [33] including lasers [34,35]. This quantum entanglement becomes accessible if an ordered (pulsed) stream of single photons is used, and enables production of linear cluster states, which has been realized recently [16,17], and feed-forward or fast modulators [14,[36][37][38] can be used to produce even more complex quantum states. We want to add that also lasers produce only approximately coherent states with entanglement of the stimulated photons via the gain medium [39][40][41][42], which is in practice inaccessible due to the impossibility of monitoring every quantum interaction in the system [43].…”

Semiconductor single-photon sources: progresses and applications

“…The QD sources are also very interesting from the perspective of creating new photonic states in which several single photons are entangled [9]. Some of these states, such as the so-called "cluster-states" are an important universal resource quantum computing, which offer a scalable path to large-scale, fault-tolerant quantum computing.…”

Multidimensional cluster states using a single spin-photon interface coupled strongly to an intrinsic nuclear register

“…In particular, multidimensional cluster states enable universal measurement-based quantum computation [4][5][6] and measurement-based quantum repeaters for long range quantum communication [14,15]. Photonic cluster states have been realised via both probabilistic entanglement schemes, using spontaneous parametric downconversion [16][17][18][19][20][21][22] and delay lines [23], as well as via deterministic entanglement schemes using squeezed light and non-gaussian measurements [24], and using quantum-dot (QD) spin to single-photon interfaces [25,26].…”