High-fidelity multi-photon-entangled cluster state with solid-state quantum emitters in photonic nanostructures

Abstract

We show that quantum dots in photonic nanostructures provide a highly promising platform for deterministic generation of entangled multiphoton states. Our approach utilizes periodic driving of a quantum-dot based emitter and an efficient light-matter interface enabled by a photonic crystal waveguide. We assess the quality of the photonic states produced from a real system by including all experimentally relevant imperfections. Importantly, the protocol is robust against the nuclear spin bath dynamics due to a naturally built-in refocussing method reminiscent to spin echo. We demonstrate the feasibility of producing the Greenberger-Horne-Zeilinger and one-dimensional cluster states with fidelities and generation rates exceeding those achieved with conventional 'fusion' methods in current state-of-the-art experiments. The proposed hardware constitutes a scalable and resource-efficient approach towards implementation of measurement-based quantum communication and computing.

Fidelity of time-bin entangled multi-photon states from a quantum emitter

“…As we discuss here and in the companion paper [47], the considered time-bin generation protocol appears to be a particularly promising approach for the sequential production of entangled photons from quantum dot emitters. Here it is highly appealing that our analysis shows that the output state is insensitive to a number of slow drifts of experimental parameters.…”

A Source of Indistinguishable Time-Bin Entangled Photons from a Waveguide-Embedded Quantum Dot

“…[11], where the use of dark-exciton states and non-resonant excitation enabled the explicit demonstration of three-qubit entanglement and extrapolation to five qubits. Nonetheless, the further scalability of multi-photon entanglement sources has been an open question so far only addressed theoretically [12,13]. A key feature is the generation of high-fidelity multi-photon entanglement while preserving photon indistinguishability; a crucial requirement for fusion-based photonic quantum computing [1,14].…”

“…The protocol is analyzed in Refs. [12,13] and the first experimental steps were implemented with a micropillar QD source [15] while spin-photon Bell-state generation was realized with nitrogen-vacancy centers [16,17]. Contrary to the Lindner-Rudolph protocol, we apply strong magnetic fields which permit the use of spin-echo pulses and render the protocol insensitive to spin-dephasing [12].…”

“…The remaining contribution is likely a result of multi-photon emission owing to the fast, Purcell enhanced decay rate γ 0 = (γ x + γ y ) = 2.54 ns −1 and the FWHM duration of the π-pulse T opt = 35 ps. T opt represents a trade-off [12,13] between multi-photon emission (minimized for T opt γ −1 0 ) and unwanted excitation of |⇓ ↔ |↓⇑⇓ (minimized for T opt ∆ −1 0 ). A larger magnetic field will increase ∆ 0 and permit a shorter T opt and thus reduced g (2) (0).…”

“…Our insights from theory and simulation show a clear path towards improving the fidelity with the quality of spin rotations requiring the most attention. Indeed, given realistic PCW parameters and greatly enhanced Raman pulses we expect to reach an error level of 2.1% per emitted photon [13]. The generalization to more photons is straightforward and only requires additional rotation and excitation pulses to create a multi-photon GHZ or 1D-cluster state with photonic qubits emitted every 28 ns.…”