Wisconsin Quantum Institute

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Events on Tuesday, May 3rd, 2022

PME Distinguished Quantum Colloquium Series
Quantum network technology: the second life of rare-earth crystals
Time: 10:00 am
Place: for zoom link:
Speaker: Wolfgang Tittel, QuTech and Kavli Institute of Nanoscience, Delft Technical University, The Netherlands
Abstract: Starting with the demonstration of lasing more than 50 years ago, the special properties of rare-earth crystals and glasses have enabled the development of numerous solid-state lasers and amplifiers, which are crucial for the functioning of today’s Internet. As a fascinating generalization of their use in optical communication infrastructure, it became clear during the past decade that, when cooled to a few Kelvin, rare-earth crystals also promise the creation of technology for quantum communication networks.

I will discuss recent advances towards the development of key ingredients of such networks: the creation of single photons using individual rare-earth ions coupled to nano-photonic cavities, as well as the reversible storage of quantum states of light in large ensembles of rare-earth ions. This work is not only interesting from a fundamental point of view, but furthermore paves the path towards a quantum repeater, which will ultimately enable quantum communications over arbitrary distances.
Host: PME/UChicago
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Simulation of some Open Quantum Systems on Near-term Quantum Computers
Time: 11:00 am
Place: virtual, for joining info see:
Speaker: Barbara A. Jones, Quantum Applications in Physical and Life Sciences, IBM Research Almaden
Abstract: Open quantum systems are everywhere in real life, whether it is systems exposed to temperature, electric field, or anything that causes dissipation and/or driving. I will be describing a few such systems that we have simulated on quantum computing hardware, which turns out to be an excellent platform for such simulations. In the first, we use the dissipation naturally occurring in superconducting qubits to map to the heat and relaxation-caused dissipation in an experimental system. This system is one of radical pairs of molecules in solution, caused by excitation of the solution with a radiation burst. The system oscillates between singlet and triplet, with a decay constant at high and low field that we map to that of the quantum computer. We get excellent agreement with experimental results out to many time steps.[1) The second set of hardware experiments were done on a model system, the Hubbard model, in two limiting cases.[2] In the noninteracting, infinite system, we are able to perform 1000 Trotter steps without decay of the measured quantity, a calculation that involved hundreds of CNOT gates. This illustrates the potential for such driven, dissipative system for simulation on a quantum computer. In the second version of the Hubbard model, we go to the opposite limit, and look at the Hubbard ‘atom” in a magnetic field and finite temperature. We are able to calculate quite accurately several physical properties of this system. I will conclude with some remarks about the promise of open quantum systems and of quantum computing in general.
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