Researchers: Satvik Singh, Nilanjana Datta
Can a noisy quantum channel be used to transmit quantum information reliably from a sender to a receiver? Answering this fundamental question has proved to be extremely difficult, despite years of research. Some noisy channels are known to have zero quantum capacity, i.e., it is impossible to send any quantum information reliably through them. However, our poor understanding of the set of zero capacity quantum channels, and the lack of a systematic procedure to determine whether a given channel has positive capacity, has led to the intractability of the above question. My recent research work with Prof. Nilanjana Datta at Cambridge is an attempt to solve the stated problem by devising a simple perturbative strategy to detect positive quantum capacities of quantum channels. Our analysis reveals that a channel’s ability to transmit information is intimately connected to the relative sizes of its input, output, and environment spaces. We exploit this link to develop easy tests which can be used to detect positivity of quantum channel capacities simply by comparing the channels’ input, output, and environment dimensions.