In quantum mechanics, particles do not have a precise position but are delocalized within a certain length. For certain quantum information applications, this length is usually neglected but we managed to take it into account for a large class of interesting processes and found that it cannot always be neglected. In particular, for such processes, quantum information is usually based on the manipulation of the internal states of these particles. You can imagine that each particle can be red or blue and we encode information on them based on their color, so that, for example, blue stands for the bit “zero” and red for the bit “one”. Operations on these quantum bits (qubits) can be faulty due to the presence of the environment but also because of the length of the particle itself. We managed to derive simple formulas to characterize the “faultiness” due to the particle’s length when this is still not too large.

Our research was published on PRL: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.132.220403