QUROPE Quantum Information Processing and Communication in Europe

The latest developments of the field are pointing to several future fundamental challenges that need to be thoroughly addressed:

• Quantum simulators. The approach to scalability characterizing special purpose quantum computers - quantum simulators - will be the first one in delivering a device capable to operate on quantum many-particle systems, and to extract useful numbers out of them [1]. The challenge in this case will be to improve the simulation capabilities of such devices, moving from condensed-matter theoretical models towards the simulation of materials and/or chemical compounds.
• Hybrid systems. Currently we are witnessing the birth of a new quantum paradigm that unifies atomic, molecular, optical (AMO) and condensed matter physics. It combines the advantages of different specific realizations of quantum bit systems to realize essential building blocks such as memories, repeaters, and interconnects [2]. There is therefore a clear need to bring hybrid technologies past the proof-of-principle stage, by bridging AMO systems with condensed matter systems in order to
  • Develop devices interconnecting different qubit ‘memories’ and quantum information carriers, in order to develop quantum networks composed of many nodes and channels;
  • Develop a working quantum repeater for bringing quantum communications to a global scale (the "quantum internet" [3]).
• Coherent operations with multiple qubits. High qubits densities entail a new set of problems with respect to those encountered in single and two-qubit operations (e.g., a more complex and noisier environment for carrying out quantum operations, which includes cross-talk from nearby qubits and their control, coupling, and readout systems). These problems (which can be specific to a particular qubit implementation or common to several of them) have to be identified, explored, and solved, possibly implementing demonstration algorithms [4].
• Quantum technologies. Novel practical devices exploiting entanglement as a resource [5], such as quantum sensing, imaging, measurement, and communication technologies, need to be investigated, in view of expanding their field of applicability towards new unprecedented directions (see examples in the next section).
• Improvement and optimization of existing platforms. A major goal of the field will be finally to improve and push the limits of the existing platforms and technologies [6]. The most promising systems need to be identified and reliable fault-tolerant gates and architectures proving their scalability to tens/hundreds of qubits developed.

The challenges outlined above are to be considered both experimental and theoretical: Theory, besides finding and investigating fundamentally new techniques (e.g., quantum feedback and quantum optimal control) algorithms and protocols for computing and communicating, and opening new multidisciplinary research directions (such as the recent studies on the potential exploitation of quantum effects in biological systems), must in fact guide and support experimental developments, covering the whole range of physical systems and technologies.