JQI-QuICS-CMTC Seminar

"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.

We generate bright, two-mode, intensity-difference squeezed light from four-wave mixing (4WM) in Rb vapor using Ti:Sapphire laser system. We achieve squeezing at frequencies below 10 Hz via dual-seeded 4WM. However, we notice that there is excess noise at low frequencies for the dual-seeded scheme due to the two-beam coupling mechanism. This noise can be avoided by making sure the two probe seeds do not intersect each other in the pump region.

It has been experimentally established that the occurrence of charge density waves is a common feature of various under-doped cuprate superconducting compounds. The observed states, which are often found in the form of bond density waves (BDW), often occur in a temperature regime immediately above the superconducting transition temperature.

Indistinguishable photon pairs and their quantum interference is a fundamental resource enabling many quantum applications such as quantum teleportation, quantum metrology, quantum communications and quantum computing. There is a growing need to generate these photon sources on-chip to create the next-generation integrated nano-photonic devices. Photon pairs are commonly produced using spontaneous parametric down-conversion (SPDC) or spontaneous-four wave mixing(SFWM).

The Harper-Hofstadter model describes particles in two-dimensional (2D) lattices subjected to a uniform magnetic field. Ultracold atomic gases in optical lattices are an ideal platform to study this model, thanks to their capability for realizing large and tunable magnetic fluxes per lattice plaquette. We experimentally assembled such a 2D lattice rolled into a long tube, just 3-site around, thereby realizing periodic boundary conditions. These three sites were constructed from a synthetic dimension built from the atoms’ internal degrees of freedom.

Topological band theory was developed to predict and explain robust features in the ground state electronic structure of insulators and superconductors. A topological material is characterized by gapless modes localized at the boundary of the sample, which dictate the low-energy response. What are the fate of these edge modes when the system starts to couple to an environment? In this talk, I will present a topological classification [1] applicable to open fermionic systems governed by a general class of Lindblad master equations.

Engineering and probing the topological order is an outstanding challenge in the current quantum simulators and of fundamental importance in the condensed matter physics. A great experimental efforts have been devoted to engineering strongly-correlated system and the topologically non-trivial band structure which makes the realization of the fractional quantum Hall liquid in the quantum simulators possible in the near future.

Suppose we know densities of eigenvalues/energy levels of two Hamiltonians HA and HB. Can we find the eigenvalue distribution of the joint Hamiltonian HA+HB? Free probability theory (FPT) answers this question under certain conditions. My goal is to show that this result is helpful in physical problems, especially finding the energy gap and predicting quantum phase transitions.

Topological order can be found in a wide range of physical systems, from crystalline solids, photonic meta-materials and even atmospheric waves to optomechanic, acoustic and atomic systems. Topological systems are a robust foundation for creating quantized channels for transporting electrical current, light, and atmospheric disturbances. These topological effects are quantified in terms of integer-valued invariants, such as the Chern number, applicable to the quantum Hall effect, or the Z2 invariant suitable for topological insulators.

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