Seminar

We derive general results relating revivals in the dynamics of quantum many-body systems to the entanglement properties of energy eigenstates. For a lattice system of N sites initialized in a low-entangled and short-range correlated state, our results show that a perfect revival of the state after a time at most poly(N) implies the existence of "quantum many-body scars", whose number grows at least as the square root of N up to poly-logarithmic factors.

I will present our recent advances in the formal verification of post-quantum security. Our framework includes a logic for reasoning about quantum programs (qRHL, quantum relational Hoare logic) and a tool for computer-aided verification in qRHL. We have used this framework to verify the post-quantum security of the Fujisaki-Okamoto transform for building encryption schemes. I will give an overview of the logical foundations and of our experiences when verifying a real-life cryptosystem.

The first part of this talk will introduce generalized Jordan–Wigner transformation on arbitrary triangulation of any manifold in 2d, 3d, and general dimensions. This gives a duality between all fermionic systems and a new class of Z2 lattice gauge theories. This map preserves the locality and has an explicit dependence on the second Stiefel–Whitney class and a choice of spin structure on the manifold.

Fault-tolerant gate sets whose generators belong to the Clifford hierarchy form the basis of many protocols for scalable quantum computing architectures. At the beginning of the decade, number-theoretic techniques were employed to analyze circuits over these gate sets on single qubits, providing the basis for a number of state-of-the-art quantum compiling algorithms. In this dissertation, I further this program by employing number-theoretic techniques for higher-dimensional gate sets on both qudit and multi-qubit circuits.
 

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.

Quantum teleportation is one of the fundamental building blocks of
quantum Shannon theory. The original teleportation protocol is an
exact protocol and amazingly simple, but it requires a non-trivial
correction operation to make it work. Port-based teleportation (PBT)
is an approximate variant of teleportation with a simple correction
operation that renders the protocol unitarily covariant. This property
enables applications such as universal programmable quantum

The unprecedented control of synthetic quantum systems allows to tackle outstanding questions from high-energy physics, such as the non-equilibrium dynamics of gauge theories, using quantum simulators. In this talk, I will first discuss dynamical topological transitions in quantum electrodynamics (QED) in one spatial dimension [1], which bear similarities with the physics of topological insulators. This phenomenon is accessible within our proposals to microscopically engineer the Hamiltonian of lattice QED with a mixture of ultracold gases [2].

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).

Quantum technologies fundamentally rely on quantum control, measurement, and feedback; however, a general understanding of many-body quantum dynamics under these conditions remains in its early stages.  Such studies may provide insight into the dynamics of quantum computers undergoing active quantum error correction while running nontrivial quantum algorithms, as well as point to a more general understanding of the transition from quantum to classical physics in many-body systems.  Measurement-induced transitions are a recently uncovered class of critical phenomena that