The development of a quantum communication network will require sources that efficiently emit single photons. Now, using a new lithography technique that garnered a silver CNRS medal in 2014, it has recently proved possible to fabricate these sources using quantum dots (QDs), that is, artificial solid-state atoms. Performed at cryogenic temperatures, this technique makes it possible to position a single QD in the middle of an optical microcavity with nanometric precision.
Quantum communication in free space is the next challenge of telecommunications. Since we want to determine the outcome of a quantum communication by means of single photons, we must understand how a single photon interacts with the atmosphere. In this brief article, some simulation results for realistic and generic atmospheric conditions are reported and discussed.
We propose a passively self-error-rejecting single-qubit transmission scheme for an arbitrary polarization state of a single qubit over a collective-noise channel, without resorting to additional qubits and entanglement. By splitting a single qubit into some wavepackets with some Mach-Zehnder interferometers, we can obtain an uncorrupted state with a success probability approaching 100% via postselection in different time bins, independent of the parameters of collective noise. It is simpler and more flexible than the schemes utilizing decoherence-free subspace and those with additional qubits. One can directly apply this scheme to almost all quantum communication protocols based on single photons or entangled photon systems against a collective noise.
Ultrabright single-photon sources