1,425 research outputs found
Phase boundaries in deterministic dense coding
We consider dense coding with partially entangled states on bipartite systems
of dimension , studying the conditions under which a given number of
messages, , can be deterministically transmitted. It is known that the
largest Schmidt coefficient, , must obey the bound , and considerable empirical evidence points to the conclusion that there
exist states satisfying for every and except the
special cases and . We provide additional conditions under
which this bound cannot be reached -- that is, when it must be that
-- yielding insight into the shapes of boundaries separating
entangled states that allow messages from those that allow only . We
also show that these conclusions hold no matter what operations are used for
the encoding, and in so doing, identify circumstances under which unitary
encoding is strictly better than non-unitary.Comment: 7 pages, 1 figur
Optimal Design Of English Auctions With Discrete Bid Levels
This paper considers a form of ascending price English auction widely used in both live and online auctions. This discrete bid auction requires that the bidders submit bids at predetermined discrete bid levels, and thus, there exists a minimal increment by which the bid price may be raised. In contrast, the academic literature of optimal auction design deals almost solely with continuous bid auctions. As a result, there is little practical guidance as to how an auctioneer, seeking to maximize its revenue, should determine the number and value of these discrete bid levels, and it is this omission that is addressed here. To this end, a model of a discrete bid auction from the literature is considered, and an expression for the expected revenue of this auction is derived. This expression is used to determine both numerical and analytical solutions for the optimal bid levels, and uniform and exponential bidder’s valuation distributions are compared. Finally, the limiting case where the number of discrete bid levels is large is considered. An analytical expression for the distribution of the optimal discrete bid levels is derived, and an intuitive understanding of how this distribution maximizes the revenue of the auction is developed
Study of localization in the quantum sawtooth map emulated on a quantum information processor
Quantum computers will be unique tools for understanding complex quantum
systems. We report an experimental implementation of a sensitive, quantum
coherence-dependent localization phenomenon on a quantum information processor
(QIP). The localization effect was studied by emulating the dynamics of the
quantum sawtooth map in the perturbative regime on a three-qubit QIP. Our
results show that the width of the probability distribution in momentum space
remained essentially unchanged with successive iterations of the sawtooth map,
a result that is consistent with localization. The height of the peak relative
to the baseline of the probability distribution did change, a result that is
consistent with our QIP being an ensemble of quantum systems with a
distribution of errors over the ensemble. We further show that the previously
measured distributions of control errors correctly account for the observed
changes in the probability distribution.Comment: 20 pages, 9 figure
The Mass-Radius Relation Of Young Stars. I. Usco 5, An M4.5 Eclipsing Binary In Upper Scorpius Observed By K2
We present the discovery that UScoCTIO 5, a known spectroscopic binary in the Upper Scorpius star-forming region (P = 34 days, M-tot sin(i) = 0.64M(circle dot)), is an eclipsing system with both primary and secondary eclipses apparent in K2 light curves obtained during Campaign 2. We have simultaneously fit the eclipse profiles from the K2 light curves and the existing RV data to demonstrate that UScoCTIO 5 consists of a pair of nearly identical M4.5 stars with M-A = 0.329 +/- 0.002 M-circle dot, R-A = 0.834 +/- 0.006 R-circle dot, M-B = 0.317 +/- 0.002 M-circle dot, and R-B = 0.810 +/- 0.006 R-circle dot. The radii are broadly consistent with pre-main-sequence ages predicted by stellar evolutionary models, but none agree to within the uncertainties. All models predict systematically incorrect masses at the 25%-50% level for the HR diagram position of these mid-M dwarfs, suggesting significant modifications to mass-dependent outcomes of star and planet formation. The form of the discrepancy for most model sets is not that they predict luminosities that are too low, but rather that they predict temperatures that are too high, suggesting that the models do not fully encompass the physics of energy transport (via convection and/or missing opacities) and/or a miscalibration of the SpT-T-eff scale. The simplest modification to the models (changing T-eff to match observations) would yield an older age for this system, in line with the recently proposed older age of Upper Scorpius (tau similar to 11 Myr).NASA Science Mission directorateW. M. Keck FoundationAstronom
The Effect of Tourniquet Use and Sterile CO2 Gas Bone Preparation on Cement Penetration in Primary Total Knee Arthroplasty
Introduction
Tourniquetless total knee arthroplasty (TKA) is experiencing resurgence in popularity due to potential pain control benefits. Further, optimal cement technique and implant fixation remain paramount to long-term cemented TKA success, as aseptic loosening continues to be a leading cause of revision. The purpose of this study was to determine how tourniquet use and/or novel bone preparation using sterile, compressed carbon dioxide (CO2) gas affected cement penetration in TKA.
Methods
A retrospective review was performed on 303 consecutive primary TKAs with the same implant in three groups: (1) a tourniquet without sterile CO2 compressed gas used for bone preparation, (2) no tourniquet with CO2 gas, and (3) tourniquet use and CO2 gas bone preparation. Cement penetration was measured on radiographs by two independent, blinded raters across seven zones defined by the Knee Society Radiographic Evaluation System.
Results
The three groups did not differ on age, BMI, or sex (p≥0.1). Cement penetration was greater in six of seven zones with significantly greater cement penetration in three zones (Tibial AP Zone 2, Femoral Lateral Zones 3A and 3P) in groups that utilized CO2 gas bone preparation compared to the tourniquet only group (p≤0.039).
Conclusion
Bone prepared with CO2 gas showed significantly more cement penetration in three zones with greater cancellous bone. The results suggest use of CO2 gas bone preparation may achieve greater cement penetration than using a tourniquet with lavage only
Pairing in fermionic systems: A quantum information perspective
The notion of "paired" fermions is central to important condensed matter
phenomena such as superconductivity and superfluidity. While the concept is
widely used and its physical meaning is clear there exists no systematic and
mathematical theory of pairing which would allow to unambiguously characterize
and systematically detect paired states. We propose a definition of pairing and
develop methods for its detection and quantification applicable to current
experimental setups. Pairing is shown to be a quantum correlation different
from entanglement, giving further understanding in the structure of highly
correlated quantum systems. In addition, we will show the resource character of
paired states for precision metrology, proving that the BCS states allow phase
measurements at the Heisenberg limit.Comment: 23 pages, 4 figure
Is There Benefit in Keeping Early Discharge Patients Overnight After Total Joint Arthroplasty?
Introduction: In recent years, cost containment relative to patent safety and quality of care for total joint arthroplasty (TJA) has been a key focus for the Centers for Medicare and Medicaid Services (CMS) spawning significant research and programmatic change, including a move toward early discharge and outpatient TJA. TJA outpatients receive few, if any, medical interventions prior to discharge, but the type and quantity of medical interventions provided for TJA patients who stay overnight in the hospital is unknown. This study quantified the nature, frequency, and outcome of interventions occurring overnight after primary TJA.
Methods: 1,725 consecutive primary unilateral TJAs performed between 2012 and 2017 by a single surgeon in a rapid-discharge program, managed by a perioperative internal medicine specialist, were reviewed. Medical records were examined for diagnostic tests, treatments, and procedures performed, results of interventions, and all-cause readmissions. Recorded interventions included any that varied from the preoperative treatment plan, were beyond standard-of-care, and could not be completed at home.
Results: 759 patients were discharged on postoperative day one. 84% (641/759) received no medical interventions during their overnight hospital stay. Twelve (1.6%) received diagnostic tests, 90 (11.9%) received treatments, and 29 (3.8%) received procedures. 92% (11/12) of diagnostic tests were negative, 66% of 100 treatments in 90 patients were intravenous fluids for oliguria or hypotension, and all procedures were in/out catheterizations for urinary retention. 90-day all cause readmission rates were similar in patients who received (2.5%) and did not receive (3.3%) a clinical intervention.
Conclusion: The majority of patients received no overnight interventions, suggesting unnecessary costly hospitalization. The most common issues addressed were oliguria, urinary retention, and hypotension. Protocols to prevent these conditions would facilitate outpatient TJA, improve patient safety, and reduce costs.This research was supported by the Indiana University Health – Indiana School of Medicine Strategic Research Initiative
Phase structure of the massive chiral Gross-Neveu model from Hartree-Fock
The phase diagram of the massive chiral Gross-Neveu model (the massive
Nambu-Jona-Lasinio model in 1+1 dimensions) is constructed. In the large N
limit, the Hartree-Fock approach can be used. We find numerically a chiral
crystal phase separated from a massive Fermi gas phase by a 1st order
transition. Using perturbation theory, we also construct the critical sheet
where the homogeneous phase becomes unstable in a 2nd order transition. A
tricritical curve is located. The phase diagram is mapped out as a function of
fermion mass, chemical potential and temperature and compared with the one of
the discrete chiral Gross-Neveu model. As a by-product, we illustrate the
crystal structure of matter at zero temperature for various densities and
fermion masses.Comment: 12 pages, 16 figure
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