472 research outputs found
Remote preparation of quantum states
Remote state preparation is the variant of quantum state teleportation in
which the sender knows the quantum state to be communicated. The original paper
introducing teleportation established minimal requirements for classical
communication and entanglement but the corresponding limits for remote state
preparation have remained unknown until now: previous work has shown, however,
that it not only requires less classical communication but also gives rise to a
trade-off between these two resources in the appropriate setting. We discuss
this problem from first principles, including the various choices one may
follow in the definitions of the actual resources. Our main result is a general
method of remote state preparation for arbitrary states of many qubits, at a
cost of 1 bit of classical communication and 1 bit of entanglement per qubit
sent. In this "universal" formulation, these ebit and cbit requirements are
shown to be simultaneously optimal by exhibiting a dichotomy. Our protocol then
yields the exact trade-off curve for arbitrary ensembles of pure states and
pure entangled states (including the case of incomplete knowledge of the
ensemble probabilities), based on the recently established quantum-classical
trade-off for quantum data compression. The paper includes an extensive
discussion of our results, including the impact of the choice of model on the
resources, the topic of obliviousness, and an application to private quantum
channels and quantum data hiding.Comment: 21 pages plus 2 figures (eps), revtex4. v2 corrects some errors and
adds obliviousness discussion. v3 has section VI C deleted and various minor
oversights correcte
Financial Crisis and the Comovements of Housing Sub-markets: Do relationships change after a crisis?
This study of the co-movements of the transaction prices and trading volumes reveal that the mean correlation of prices, and trading volumes alike, among different housing sub-markets increases during the market boom. After a financial crisis, the correlations drop dramatically and stay low. The distribution of the correlations changes from skewed to symmetric. All these coincide with the increase in the total variance of prices, as well as the share of the idiosyncratic component in the total variance after the crisis. These findings are consistent to a family of theories which emphasize on âregime switchâ in expectation.financial crisis; hedonic pricing; structural break; evolution of valuation; rolling regression
Random subspaces for encryption based on a private shared Cartesian frame
A private shared Cartesian frame is a novel form of private shared
correlation that allows for both private classical and quantum communication.
Cryptography using a private shared Cartesian frame has the remarkable property
that asymptotically, if perfect privacy is demanded, the private classical
capacity is three times the private quantum capacity. We demonstrate that if
the requirement for perfect privacy is relaxed, then it is possible to use the
properties of random subspaces to nearly triple the private quantum capacity,
almost closing the gap between the private classical and quantum capacities.Comment: 9 pages, published versio
Staggered local density-of-states around the vortex in underdoped cuprates
We have studied a single vortex with the staggered flux (SF) core based on
the SU(2) slave-boson theory of high superconductors. We find that
whereas the center in the vortex core is a SF state, as one moves away from the
core center, a correlated staggered modulation of the hopping amplitude
and pairing amplitude becomes predominant. We predict that in this
region, the local density-of-states (LDOS) exhibits staggered modulation when
measured on the bonds, which may be directly detected by STM experiments.Comment: 4 pages, 3 figure
Financial Crisis and the Comovements of Housing Sub-markets: Do relationships change after a crisis?
This study of the co-movements of the transaction prices and trading volumes reveal that the mean correlation of prices, and trading volumes alike, among different housing sub-markets increases during the market boom. After a financial crisis, the correlations drop dramatically and stay low. The distribution of the correlations changes from skewed to symmetric. All these coincide with the increase in the total variance of prices, as well as the share of the idiosyncratic component in the total variance after the crisis. These findings are consistent to a family of theories which emphasize on âregime switchâ in expectation
Financial Crisis and the Comovements of Housing Sub-markets: Do relationships change after a crisis?
This study of the co-movements of the transaction prices and trading volumes reveal that the mean correlation of prices, and trading volumes alike, among different housing sub-markets increases during the market boom. After a financial crisis, the correlations drop dramatically and stay low. The distribution of the correlations changes from skewed to symmetric. All these coincide with the increase in the total variance of prices, as well as the share of the idiosyncratic component in the total variance after the crisis. These findings are consistent to a family of theories which emphasize on âregime switchâ in expectation
Octopamine Neuromodulation Regulates Gr32a-Linked Aggression and Courtship Pathways in \u3ci\u3eDrosophila\u3c/i\u3e Males
Chemosensory pheromonal information regulates aggression and reproduction in many species, but how pheromonal signals are transduced to reliably produce behavior is not well understood. Here we demonstrate that the pheromonal signals detected by Gr32a-expressing chemosensory neurons to enhance male aggression are filtered through octopamine (OA, invertebrate equivalent of norepinephrine) neurons. Using behavioral assays, we find males lacking both octopamine and Gr32a gustatory receptors exhibit parallel delays in the onset of aggression and reductions in aggression. Physiological and anatomical experiments identify Gr32a to octopamine neuron synaptic and functional connections in the suboesophageal ganglion. Refining the Gr32a-expressing population indicates that mouth Gr32a neurons promote male aggression and form synaptic contacts with OA neurons. By restricting the monoamine neuron target population, we show that three previously identified OA-FruM neurons involved in behavioral choice are among the Gr32a-OA connections. Our findings demonstrate that octopaminergic neuromodulatory neurons function as early as a second-order step in this chemosensory-driven male social behavior pathway
Aspects of generic entanglement
We study entanglement and other correlation properties of random states in
high-dimensional bipartite systems. These correlations are quantified by
parameters that are subject to the "concentration of measure" phenomenon,
meaning that on a large-probability set these parameters are close to their
expectation. For the entropy of entanglement, this has the counterintuitive
consequence that there exist large subspaces in which all pure states are close
to maximally entangled. This, in turn, implies the existence of mixed states
with entanglement of formation near that of a maximally entangled state, but
with negligible quantum mutual information and, therefore, negligible
distillable entanglement, secret key, and common randomness. It also implies a
very strong locking effect for the entanglement of formation: its value can
jump from maximal to near zero by tracing over a number of qubits negligible
compared to the size of total system. Furthermore, such properties are generic.
Similar phenomena are observed for random multiparty states, leading us to
speculate on the possibility that the theory of entanglement is much simplified
when restricted to asymptotically generic states. Further consequences of our
results include a complete derandomization of the protocol for universal
superdense coding of quantum states.Comment: 22 pages, 1 figure, 1 tabl
Signature of the staggered flux state around a superconducting vortex in underdoped cuprates
Based on the SU(2) lattice gauge theory formulation of the t-J model, we
discuss possible signature of the unit cell doubling associated with the
staggered flux (SF) state in the lightly doped spin liquid. Although the SF
state appears only dynamically in a uniform d-wave superconducting (SC) state,
a topological defect [SU(2) vortex] freezes the SF state inside the vortex
core. Consequently, the unit cell doubling shows up in the hopping
() and pairing () order parameters of physical
electrons. We find that whereas the center in the vortex core is a SF state, as
one moves away from the core center, a correlated staggered modulation of
and becomes predominant. We predict that over the
region outside the core and inside the internal gauge field penetration depth
around a vortex center, the local density-of-states (LDOS) exhibits staggered
peak-dip (SPD) structure inside the V-shaped profile when measured on the
bonds. The SPD structure has its direct origin in the unit cell doubling
associated with the SF core and the robust topological texture, which has
little to do with the symmetry of the d-wave order parameter. Therefore the
structure may survive the tunneling matrix element effects and easily be
detected by STM experiment.Comment: 27 pages, 14 figures in GIF format, typo correcte
A 50-Year-Old Woman with Recurrent Generalised Seizures
Ronald Ma and colleagues discuss the differential diagnosis, investigation, and management of this patient
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