Yesterday at CQT Jonathan Simon from Stanford University gave a wonderful colloquium talk on "Many-body Ramsey Spectroscopy in the Bose Hubbard Model," covering experimental studies of strongly interacting quantum fluids of photons in arrays of superconducting qubits, spanning work from 2019 on the preparation of photonic Mott insulating states to ongoing studies of entangled many-body states of light.
A good colloquium talk should understandable to a broad audience (ideally, including undergraduates) while still going into enough depth to keep specialists in the topic interested. If you cannot frame your research in terms of some simplified model, chances are you do not yet fully understand it.
Simon did this using the neat example of emergence in 2D point clouds: observing non-trivial emergent properties requires three key ingredients: many particles, interactions between the particles, and dissipation (in this case, friction) to allow the system to relax to some ordered state. When all three are included, the cloud self-organizes into a triangular lattice with properties qualitatively different from those of the individual constituent particles, supporting low energy vibrational modes (phonons).
Typically, a colloquium talk will cover research spanning several years. It is important to have some clear common motivation. In this case, the question of how to make quantum states of light exhibit similar emergent properties? Three ingredients are required: give photons an effective mass, achieve strong photon-photon interactions, and introduce a suitable form of dissipation that allows the system to relax to some interesting equilibrium state while preserving non-trivial many-particle effects.
After this framing, the talk went deep into how these ingredients can be realized using arrays of superconducting qubits, and how the relevant dimensionless quantities (interaction strength vs hopping strength vs photon lifetime) compare to other platforms, such as cold atoms (handy, given the mix of expertise in the audience).
The talk finished with a vision for the future - to connect this "photonic quantum simulator" to a small-scale quantum processor to test NISQ-friendly algorithms, such as shadow tomography of many-body quantum states.
A recording will probably be uploaded to the CQT Youtube page later. In the meantime, related talks given at JQI and Munich are already available online!
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