Tomography-based Quantum Key Distribution

TL;DR

This paper extends the use of quantum state tomography to higher-dimensional qudit-based quantum key distribution, demonstrating improved key rates over standard protocols and comparing favorably with reference-frame-independent methods.

Contribution

It generalizes tomography-based QKD to prime-dimensional qudits and shows its advantages over standard and reference-frame-independent protocols.

Findings

Tomography-based QKD improves key rates for prime-dimensional qudits.

The protocol outperforms reference-frame-independent QKD in most channels.

Experimental application to OAM encoding demonstrates practical benefits.

Abstract

It has previously been shown that quantum state tomography can be used to increase the key rate of quantum key distribution (QKD) for the special case of qubits (i.e.,d=2). Here, we consider the case of higher dimensions, i.e., qudits, and show that, for a prime number d>2, quantum state tomography can also improve the key rate of d-dimensional qudit-based QKD schemes, compared to the standard (d+1)-basis protocol. We apply our results to previous QKD experiments based on OAM (orbital angular momentum) encoding and demonstrate the advantage of tomography-based QKD protocols. Moreover, we compare the key rate of tomography-based QKD protocol with reference-frame-independent QKD protocol. We show that, for a rotation channel, the two protocols give the same key rate. However, for any other channels, tomography-based QKD protocol always gives a higher key rate than reference-frame-independent QKD protocol.