Quantum cryptography with highly entangled photons from semiconductor quantum dots.

Christian Schimpf,Santanu Manna,Philip Walther,Barbara Lehner,Saimon F Covre Da Silva,Armando Rastelli,Michal Vyvlecka,Marcus Reindl,Daniel Huber

doi:10.1126/sciadv.abe8905

Abstract

Semiconductor quantum dots are capable of emitting polarization entangled photon pairs with ultralow multipair emission probability even at maximum brightness. Using a quantum dot source with a fidelity as high as 0.987(8), we implement here quantum key distribution with an average quantum bit error rate as low as 1.9% over a time span of 13 hours. For a proof of principle, the key generation is performed with the BBM92 protocol between two buildings, connected by a 350-m-long fiber, resulting in an average raw (secure) key rate of 135 bits/s (86 bits/s) for a pumping rate of 80 MHz, without resorting to time- or frequency-filtering techniques. Our work demonstrates the viability of quantum dots as light sources for entanglement-based quantum key distribution and quantum networks. By increasing the excitation rate and embedding the dots in state-of-the-art photonic structures, key generation rates in the gigabits per second range are in principle at reach.

Highlights

Our everyday communication is secured by classical encryption systems that cannot hold up against attacks from emerging quantum technology [1]
The first communication node (“Alice”) and the GaAs quantum dots (QDs)-based photon source are situated in a laboratory in the semiconductor physics building at the Johannes Kepler University campus, while the second node (“Bob”) is a mobile system placed on an office desk in the LIT Open Innovation Center (OIC) and is connected to the source by a 350-m-long single mode (SM) fiber
We have presented the implementation of quantum cryptography using a quantum key derived from near-perfectly entangled photon pairs generated by a GaAs QD obtained by droplet etching [27, 31]

Summary

Introduction

Our everyday communication is secured by classical encryption systems that cannot hold up against attacks from emerging quantum technology [1]. Quantum key distribution systems with single photons using the BB84 protocol [2], albeit being information-theoretically secure, exhibit severe security loopholes, such as splitting attacks [3]. Most of the EQKD experiments so far have been performed using photon pairs generated via the spontaneous parametric down-conversion (SPDC) process [13, 14] For those sources, the multiphoton-pair emission probability is directly coupled to the source brightness by their approximately Poissonian emission characteristics [15]. To improve the source brightness without increasing the average multiphoton number, multiplexing of single photons emitted by several weakly pumped SPDCs has been successfully demonstrated [18] In this approach, one of the photons of a pair is sacrificed to herald the presence of the other. Successful attempts of quantum teleportation [34] and entanglement swapping with QDs [11, 12] further encourage the development of QD-based quantum networks for long-haul quantum communication [10]

Methods

Results

Conclusion