JQI-QuICS-CMTC Seminar

Abstract: In this talk, I will summarise recent theoretical work on understanding nonlinear response functions in systems with interacting quasiparticles.

Abstract: Superconductivity in the limit of a vanishing bandwidth in isolated bands is a classic example of a non-perturbative problem, where BCS theory does not apply. What sets the superconducting phase stiffness, and relatedly the transition temperature, in this limit is of both fundamental and practical interest. This question has become especially relevant with the discovery of superconductivity in moiré materials.

"Mana" is a measure of the degree to which a state cannot be approximated the result of Clifford gates; consequently, it can measure both the difficulty of state preparation on a quantum computer, and the degree to which entanglement is non-Bell-pair. I will show numerical calculations of the mana of ground states of the one-dimensional Z3 Potts model, chosen for convenience, in which we find that the mana is extensive and peaked at the phase transition.

The AdS/CFT correspondence is a concrete instance ofholographic duality, where a bulk theory of quantum gravity in d+1dimensions can emerge from a conformal field theory (CFT) in ddimensions. In particular, we expect the semi-classical spacetime ofd+1 dimensions to emerge from the entanglement patterns of certainquantum states in the CFT. Therefore, it is crucial to understand whatkind of states encode such spacetime geometries and how to explicitlyreconstruct these geometries from quantum entanglement. In this talk,

Abstract: Quantum photonics provides a powerful toolbox with vastapplications ranging from quantum simulation, photonic informationprocessing, all optical universal quantum computation, secure quantuminternet as well as quantum enhanced sensing. Many of theseapplications require the integration of several complex opticalelements and material systems which pose a challenge in scalability.Integration of linear and non-linear photonics on a chip is essentialto tackle this issue leading to more compact, high bandwidth devices.

(pizza and drinks served at 12pm; talk starts at 12:10pm)
 

(pizza and drinks served at 12pm; talk starts at 12:10pm)

The interaction of a single photon with an individual two-level system is the textbook example of quantum electrodynamics. Achieving strong coupling in this system has so far required confinement of the light field inside resonators or waveguides. Experiments with Rydberg superatoms [1,2] have demonstrated the ability to realize strong coupling to a propagating light pulse containing only a few photons in free space.

Simulating the dynamics of quantum systems is an important application of quantum computers and has seen a variety of implementations on current hardware. We show that by introducing quantum gates implementing unitary transformations generated by the symmetries of the system, one can induce destructive interference between the errors from different steps of the simulation, effectively giving faster quantum simulation by symmetry protection. We derive rigorous bounds on the error of a symmetry-protected simulation algorithm and identify conditions for optimal symmetry protection.