All

We study the quantum speed limit for open quantum systems described by the
Lindblad master equation. The obtained inequality shows a trade-off relation
between the operation time and the physical quantities such as the energy
fluctuation and the entropy production. We further identify a quantity
characterizing the speed of the state transformation, which appears only when
we consider the open system dynamics in the quantum regime. When the thermal
relaxation is dominant compared to the unitary dynamics of the system, we show

We propose a physical mechanism to generate and selectively amplify
anisotropic Rudermann-Kittel-Kasuya-Yosida (RKKY) interactions between two
local spins. The idea is to combine the deflection of the carrier velocity by a
P-N interface and the locking of this velocity to the carrier spin orientation
via spin-orbit coupling. We provide analytical and numerical results to
demonstrate this mechanism on the surface of a topological insulator P-N
junction. This work identifies the P-N interface as a second knob which,

Superconducting metamaterials are a promising resource for quantum
information science. In the context of circuit QED, they provide a means to
engineer on-chip, novel dispersion relations and a band structure that could
ultimately be utilized for generating complex entangled states of quantum
circuitry, for quantum reservoir engineering, and as an element for quantum
simulation architectures. Here we report on the development and measurement at
millikelvin temperatures of a particular type of circuit metamaterial resonator

We give arguments for the existence of a thermodynamics of quantum complexity
that includes a "Second Law of Complexity". To guide us, we derive a
correspondence between the computational (circuit) complexity of a quantum
system of $K$ qubits, and the positional entropy of a related classical system
with $2^K$ degrees of freedom. We also argue that the kinetic entropy of the
classical system is equivalent to the Kolmogorov complexity of the quantum
Hamiltonian. We observe that the expected pattern of growth of the complexity

We study the quantum dynamics of many-body arrays of two-level atoms in a
driven cavity subject to collective decay and interactions mediated by the
cavity field. We work in the bad cavity limit accessible, for example, using
long-lived electronic clock states of alkaline earth atoms, for which the bare
atomic linewidth is much less than the cavity linewidth. In the absence of
interactions, our system reduces to previously studied models of collective
fluorescence. We show that while interactions do not qualitatively change the

In the process of parametric optical image amplification, images are formed
at new frequencies in addition to the amplified original image. We show that
the parametric multiplexing of optical images can be used to produce an image
with improved quality. As an example, we study the parametric amplification of
an optical image at low-frequency pumping in which multiplexed optical images
turn out to be quantum-correlated. Additional improvement is made possible by

There is evidence that Planck's constant shows statistical variations with
altitude above the earth due to Kentosh and Mohageg, and yearly systematic
changes with the orbit of the earth about the sun due to Hutchins. Many others
have postulated that the fundamental constants of nature are not constant
either locally or universally. This work is a mathematical study examining the
impact of a position dependent Planck's constant in the Schrodinger equation.

A discrete-time Quantum Walk (QW) is an operator driving the evolution of a
single particle on the lattice, through local unitaries. Some QW admit, as
their continuum limit, a well-known equation of Physics. In arXiv:1803.01015
the QW is over the honeycomb and triangular lattices, and simulates the Dirac
equation. We apply a spacetime coordinate transformation upon the lattice of
this QW, and show that it is equivalent to introducing spacetime-dependent

Banaszek, W\'odkiewicz and others
(\cite{Banaszek},\cite{Chen},\cite{Chen-Zhang}) made the surprising discovery
that Einstein-Bell locality inequalities can be violated by the two mode
squeezed vacuum by a factor $\sqrt{2}$, in spite of the fact that the state has
a positive Wigner function. I use here the more general Gleason-Kochen-Specker
assumption of non-contextuality \cite{Gleason} to express classicality. I then
derive non-contextuality Bell inequalities for correlations of $N$ pseudo spins

We investigate the performance of error mitigation via measurement of
conserved symmetries on near-term devices. We present two protocols to measure
conserved symmetries during the bulk of an experiment, and develop a zero-cost
post-processing protocol which is equivalent to a variant of the quantum
subspace expansion. We develop methods for inserting global and local symetries
into quantum algorithms, and for adjusting natural symmetries of the problem to