2,446 research outputs found
High-fidelity readout of trapped-ion qubits
We demonstrate single-shot qubit readout with fidelity sufficient for
fault-tolerant quantum computation, for two types of qubit stored in single
trapped calcium ions. For an optical qubit stored in the (4S_1/2, 3D_5/2)
levels of 40Ca+ we achieve 99.991(1)% average readout fidelity in one million
trials, using time-resolved photon counting. An adaptive measurement technique
allows 99.99% fidelity to be reached in 145us average detection time. For a
hyperfine qubit stored in the long-lived 4S_1/2 (F=3, F=4) sub-levels of 43Ca+
we propose and implement a simple and robust optical pumping scheme to transfer
the hyperfine qubit to the optical qubit, capable of a theoretical fidelity
99.95% in 10us. Experimentally we achieve 99.77(3)% net readout fidelity,
inferring at least 99.87(4)% fidelity for the transfer operation.Comment: 4 pages, 3 figures; improved readout fidelity (numerical results
changed
Recommended from our members
Lexical vs Nonlexical Cognitive Processing: Is General Solwing Domain-Specific?
Micro-evaporators for kinetic exploration of phase diagrams
We use pervaporation-based microfluidic devices to concentrate species in
aqueous solutions with spatial and temporal control of the process. Using
experiments and modelling, we quantitatively describe the advection-diffusion
behavior of the concentration field of various solutions (electrolytes,
colloids, etc) and demonstrate the potential of these devices as universal
tools for the kinetic exploration of the phases and textures that form upon
concentration
Truthful Multi-unit Procurements with Budgets
We study procurement games where each seller supplies multiple units of his
item, with a cost per unit known only to him. The buyer can purchase any number
of units from each seller, values different combinations of the items
differently, and has a budget for his total payment.
For a special class of procurement games, the {\em bounded knapsack} problem,
we show that no universally truthful budget-feasible mechanism can approximate
the optimal value of the buyer within , where is the total number of
units of all items available. We then construct a polynomial-time mechanism
that gives a -approximation for procurement games with {\em concave
additive valuations}, which include bounded knapsack as a special case. Our
mechanism is thus optimal up to a constant factor. Moreover, for the bounded
knapsack problem, given the well-known FPTAS, our results imply there is a
provable gap between the optimization domain and the mechanism design domain.
Finally, for procurement games with {\em sub-additive valuations}, we
construct a universally truthful budget-feasible mechanism that gives an
-approximation in polynomial time with a
demand oracle.Comment: To appear at WINE 201
Experimental realization of a quantum game on a one-way quantum computer
We report the first demonstration of a quantum game on an all-optical one-way
quantum computer. Following a recent theoretical proposal we implement a
quantum version of Prisoner's Dilemma, where the quantum circuit is realized by
a 4-qubit box-cluster configuration and the player's local strategies by
measurements performed on the physical qubits of the cluster. This
demonstration underlines the strength and versatility of the one-way model and
we expect that this will trigger further interest in designing quantum
protocols and algorithms to be tested in state-of-the-art cluster resources.Comment: 13 pages, 4 figure
Global and regional left ventricular myocardial deformation measures by magnetic resonance feature tracking in healthy volunteers: comparison with tagging and relevance of gender
This work was funded by a grant from the Engineering and Physical Sciences Research Council (EP/G030693/1) and supported by the Oxford British Heart Foundation Centre of Research Excellence and the National Institute for Health Research Oxford Biomedical Research Centr
Optimal Design of Robust Combinatorial Mechanisms for Substitutable Goods
In this paper we consider multidimensional mechanism design problem for
selling discrete substitutable items to a group of buyers. Previous work on
this problem mostly focus on stochastic description of valuations used by the
seller. However, in certain applications, no prior information regarding
buyers' preferences is known. To address this issue, we consider uncertain
valuations and formulate the problem in a robust optimization framework: the
objective is to minimize the maximum regret. For a special case of
revenue-maximizing pricing problem we present a solution method based on
mixed-integer linear programming formulation
Biology helps you to win a game
We present a game of interacting agents which mimics the complex dynamics
found in many natural and social systems. These agents modify their strategies
periodically, depending on their performances using genetic crossover
mechanisms, inspired by biology. We study the performances of the agents under
different conditions, and how they adapt themselves. In addition the dynamics
of the game is investigated.Comment: 4 pages including 6 figures. Uses REVTeX4. Submitted for Conference
Proceedings of the "Unconventional Applications of Statistical Physics",
Kolkat
Quantum Games
In these lecture notes we investigate the implications of the identification
of strategies with quantum operations in game theory beyond the results
presented in [J. Eisert, M. Wilkens, and M. Lewenstein, Phys. Rev. Lett. 83,
3077 (1999)]. After introducing a general framework, we study quantum games
with a classical analogue in order to flesh out the peculiarities of game
theoretical settings in the quantum domain. Special emphasis is given to a
detailed investigation of different sets of quantum strategies.Comment: 13 pages (LaTeX), 3 figure
Quantum Games and Quantum Strategies
We investigate the quantization of non-zero sum games. For the particular
case of the Prisoners' Dilemma we show that this game ceases to pose a dilemma
if quantum strategies are allowed for. We also construct a particular quantum
strategy which always gives reward if played against any classical strategy.Comment: 4 pages, 4 figures, typographic sign error in the definition of the
operator J correcte
- …