arXiv subjects

Amita Gnanapandithan

Publications and source records attributed to Amita Gnanapandithan.

3 recordsLinked to original sources

arXiv2025

Mitigating Phase Correlations in Quantum Key Distribution Using Path-Selection Modulation

Phase correlations are an under-explored vulnerability in QKD. Here, we present an experimental and simulated characterization of correlations arising from electro-optic phase encoding, over repetition rates up to the GHz level. To mitigate this vulnerability (and all side channels arising from active phase modulators), we propose a "path-selection modulation" source that eliminates the need for active phase modulation altogether. Encoding is achieved by randomly selecting between multiple paths, each path corresponding to one of the desired encoded states. Phase randomization is achieved using gain-switching. We characterize this source at a clock rate of 1 GHz.

quant-ph↗

arXiv2025

Hidden multi-dimensional modulation side channels in quantum protocols

Quantum protocols including quantum key distribution and blind quantum computing often require the preparation of quantum states of known dimensions. Here, we show that, rather surprisingly, hidden multi-dimensional modulation is often performed by practical devices. This violates the dimensional assumption in quantum protocols, thus creating side channels and security loopholes. Our work has important impacts on the security of quantum cryptographic protocols.

quant-ph↗

arXiv2021

Measurement device-independent quantum key distribution with passive, time-dependent source side-channels

While measurement-device-independent (MDI) quantum key distribution (QKD) allows two trusted parties to establish a shared secret key from a distance without needing to trust a central detection node, their quantum sources must be well-characterized, with side-channels at the source posing the greatest loophole to the protocol's security. In this paper, we identify a time-dependent side-channel in a common polarization-based QKD source that employs a Faraday mirror for phase stabilization. We apply the recently developed numerical proof technique from [Phys. Rev. A 99, 062332 (2019)] to quantify the sensitivity of the secret key rate to the quantum optical model for the side-channel, and to develop strategies to mitigate the information leakage. In particular, we find that the MDI three-state and BB84 protocols, while yielding the same key rate under ideal conditions, have diverging results in the presence of a side-channel, with BB84 proving more advantageous. While we consider only a representative case example, we expect the strategies developed and key rate analysis method to be broadly applicable to other leaky sources.

quant-ph↗