QuantumFuture Research Group focuses its objectives on the communication at the quantum limit. QuantumFuture, originally born as a strategic project of the University of Padova, has a deep expertise is in free-space quantum communication, both on ground and in Space, as well as in quantum optics and quantum key distribution.

We wish to motivate in more details why we focus our research on free-space communication, which, at present, is relatively unexplored with respect to fiber-based optical communication, but, at the same time, it is attracting an increasing interest. Two reasons can be given for this choice:

• At a fundamental level, it is a powerful tool to confirm the validity of quantum mechanics over truly large distances (also over interplanetary distances).
• At the practical level, by its intrinsic flexibility with respect to different applications context, as explained below.

Achieving the quantum limit in real-world free-space communications, in order to realize a decisive leap forward in the communication capacity, implies great difficulties in several areas, whose solutions are targeted in our objectives. Two examples of such difficulties are expounded here:

– On a fundamental physical side, any real quantum communication system, by interacting with its environment, is subject to a loss of quantum coherence. The understanding of such effects in the practical implementation of quantum channels is crucial for the optimization of the channel itself. Indeed, the design of the communication systems has to adopt an encoding scheme and an error-correcting protocol tailored to the particular channel.

– On a practical side, one has to exploit recent technologies for quantum detection and system integration. One of such field where research is very active is that of detectors for single photon counting, going on worldwide in several laboratories. Several characteristics must be carefully ascertained before a practical application of a given device: spectral response, time tagging capability, dark counts level, after-pulsing probability, and last but not least availability, reliability and cost. Our past and present experiences (see our publication) show our competence to approach such problems.

QuantumFuture is focused on the communication at the quantum limit. This subject is the physical terminus of several practical situations as:

• the very-long range communications, due to the strong signal attenuation, which reach the single photon level;
• the very high bit-rate links, due to the limitation in the input power to stay below nonlinear threshold,
• the coding of information based on the single quanta internal degrees of freedom, as in quantum cryptography or teleportation.

It is important to emphasize that within each of these contexts, the project can take advantage of the competences of the three operating units (optics, telecommunications and controls), as all share the scientific background and use common implementing techniques. We are devoting our efforts to explore the following topics:

1. Modelization of the atmospheric channel
2. Adaptive Optics Elements
3. Telescopes Definition
4. Frequency and Time Synchronization
5. Optical Communication improvement
6. Quantum Key Distribution enhancement

quantumfuture.dei.unipd.it