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