# All

We derive an effective field theory for general chaotic two-dimensional

conformal field theories with a large central charge. The theory is a specific

and calculable instance of a more general framework recently proposed in [1].

We discuss the gauge symmetries of the model and how they relate to the

Lyapunov behaviour of certain correlators. We calculate the out-of-time-ordered

correlators diagnosing quantum chaos, as well as certain more fine-grained

higher-point generalizations, using our Lorentzian effective field theory. We

We propose a branch-and-bound algorithm for minimizing a bilinear functional

of the form \[ f(X,Y) = \mathrm{tr}((X\otimes

Y)Q)+\mathrm{tr}(AX)+\mathrm{tr}(BY) , \] of pairs of Hermitian matrices

$(X,Y)$ restricted by joint semidefinite programming constraints. The

functional is parametrized by self-adjoint matrices $Q$, $A$ and $B$. This

problem generalizes that of a bilinear program, where $X$ and $Y$ belong to

polyhedra. The algorithm converges to a global optimum and yields upper and

We examine the effects of the Dzyaloshinsky-Moriya (DM) interaction on the

nonequilibrium thermodynamics in an anisotropic $XY$ spin chain, which is

driven out of equilibrium by a sudden quench of the control parameter of the

Hamiltonian. By analytically evaluating the statistical properties of the work

distribution and the irreversible entropy production, we investigate the

influences of the DM interaction on the nonequilibrium thermodynamics of the

system with different parameters at various temperatures. We find that

Certain quantum operations can be built more efficiently through a procedure

known as Repeat-Until-Success. Differently from other non-deterministic quantum

operations, this procedure provides a classical flag which certifies the

success or failure of the procedure and, in the latter case, a recovery step

allows the restoration of the quantum state to its original condition. The

procedure can then be repeated until success is achieved. After success is

certified, the RUS procedure can be equated to a coherent gate. However, this

Quantum steganography is the study of hiding secret quantum information by

encoding it into what an eavesdropper would perceive as an innocent-looking

message. Here we study an explicit steganographic encoding for a sender, Alice,

to hide a secret message in the syndromes of an error-correcting code, so that

the encoding simulates a given noisy quantum channel that Eve believes to

connect Alice and Bob. The actual physical channel connecting Alice and Bob is

We compare recently proposed methods to compute the ground state energies of

the Hamiltonian for the water molecule on a quantum computer. The methods

include the phase estimation algorithm based on Trotter decomposition, the

phase estimation algorithm based on the direct implementation of the

Hamiltonian, direct measurement based on the implementation of the Hamiltonian

and the variational quantum eigensolver. After deriving the Hamiltonian using

STO-3G basis, we first explain how each method works and then compare the

Bridging the gap between quantum software and hardware, recent research

proposed a quantum control microarchitecture QuMA which implements the quantum

microinstruction set QuMIS. However, QuMIS does not offer feedback control, and

is tightly bound to the hardware implementation. Also, as the number of qubits

grows, QuMA cannot fetch and execute instructions fast enough to apply all

operations on qubits on time. Known as the quantum operation issue rate

We propose a scheme for the quantum simulation of sub-Ohmic spin--boson

models by color centers in free-standing hexagonal boron nitride (h-BN)

membranes. The electronic spin of a color center that couples to the membrane

vibrational spectrum constitute the physical model. The spin-motion coupling is

provided by an external magnetic field gradient. In this study, we show that a

class of spectral densities can be attained by engineering geometry and

boundary conditions of the h-BN resonator. We then put our focus on two extreme

Spectral characterization is a fundamental step in the development of useful

quantum technology platforms. Here, we study an ensemble of interacting qubits

coupled to a single quantized field mode, an extended Dicke model that might be

at the heart of Bose-Einstein condensate in a cavity or circuit-QED experiments

for large and small ensemble sizes, respectively. We present a semi-classical

and quantum analysis of the model. In the semi-classical regime, we show

Enhanced sensitivity in electromagnetically induced transparency (EIT) can be

obtained by the use of noise correlation spectroscopy between the fields

involved in the process. Here, we investigate EIT in a cold ($< 1$ mK) rubidium

vapor and demonstrate sensitivity to detect weak light-induced forces on the

atoms. A theoretical model is developed and shows good agreement with our

measurements, enabling the attribution of the observed effects to the coupling