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Quantum Control Applied to Quantum Information

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Bringing on quantum information in leaps and bounds

An EU-funded research project used optimal control theory to improve quantum information (QI) processes. The theoretical work has expanded knowledge of quantum process tomography and helped to bring the reality of a quantum computer one step closer.

Digital Economy

Quantum computers, which use quantum mechanical properties such as superposition and entanglement to perform operations on data, promise vastly more powerful processing than traditional ones. In turn, they will enable scientists to run algorithms far beyond the capabilities of any binary system. However, there are two big problems with QI that need to be solved to bring about physical implementation. One is the ability to perform a desired unitary operation on a selected quantum system with very high fidelity, and the other is to preserve system coherence while performing the operation. Funded by the EU, the 'Quantum control applied to quantum information' (QOC4QIP) project developed a theoretical framework to address both issues. First, the researchers developed a general approach to treating decoherence without invoking any assumption on the system environment interaction and allowing for a non-trivial bath structure. Numerical simulations built on the existing surrogate Hamiltonian approach and required the combination of concepts from diverse areas of physics. The second part of the project — which involved collaboration between early-career and senior researchers — focused on modelling to apply optimal control algorithms to open systems. Ongoing work is continuing efforts to determine the best possible quantum-state tomography for superconducting qubits. QOC4QIP's algebraic theory has enabled much clearer classification of approaches to this field of study and made apparent areas where much investigation is incomplete. The research is being taken forward as part of larger international cooperation efforts.

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