Chirality of nanophotonic waveguide with embedded quantum emitter for unidirectional spin transfer.

M N Makhonin,R J Coles,J E Dixon,M S Skolnick,E Clarke,A M Fox,B Royall,P Kok,D M Price

doi:10.1038/ncomms11183

M N Makhonin, R J Coles + Show 7 more

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https://doi.org/10.1038/ncomms11183

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Abstract

Scalable quantum technologies may be achieved by faithful conversion between matter qubits and photonic qubits in integrated circuit geometries. Within this context, quantum dots possess well-defined spin states (matter qubits), which couple efficiently to photons. By embedding them in nanophotonic waveguides, they provide a promising platform for quantum technology implementations. In this paper, we demonstrate that the naturally occurring electromagnetic field chirality that arises in nanobeam waveguides leads to unidirectional photon emission from quantum dot spin states, with resultant in-plane transfer of matter-qubit information. The chiral behaviour occurs despite the non-chiral geometry and material of the waveguides. Using dot registration techniques, we achieve a quantum emitter deterministically positioned at a chiral point and realize spin-path conversion by design. We further show that the chiral phenomena are much more tolerant to dot position than in standard photonic crystal waveguides, exhibit spin-path readout up to 95±5% and have potential to serve as the basis of spin-logic and network implementations.

Highlights

Scalable quantum technologies may be achieved by faithful conversion between matter qubits and photonic qubits in integrated circuit geometries
An important step forward was made very recently in which directional emission was demonstrated for a quantum-dot emitter embedded within a specially engineered glide-plane waveguide[14], confirming theoretical predictions for chiral emission in photonic crystal waveguides (PhC WGs)[14,15]
We demonstrate the importance of the position of the quantum emitter, in such a way that spin-dependent directional emission is achieved

Summary

Introduction

Scalable quantum technologies may be achieved by faithful conversion between matter qubits and photonic qubits in integrated circuit geometries. We demonstrate that the naturally occurring electromagnetic field chirality that arises in nanobeam waveguides leads to unidirectional photon emission from quantum dot spin states, with resultant in-plane transfer of matter-qubit information. An important step forward was made very recently in which directional emission was demonstrated for a quantum-dot emitter embedded within a specially engineered glide-plane waveguide[14], confirming theoretical predictions for chiral emission in photonic crystal waveguides (PhC WGs)[14,15]. We achieve efficient coupling of QD exciton spin to the direction of photon emission in nanophotonic waveguides This chiral behaviour occurs even though the waveguide geometry is completely symmetric, and the dielectric material is non-chiral. The results establish a route towards the transfer and entanglement of the spin state of an emitter to a photonic qubit in an integrated network

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