508 research outputs found
Trotter24: A precision-guaranteed adaptive stepsize Trotterization for Hamiltonian simulations
Choosing an optimal time step is crucial for an efficient
Hamiltonian simulation based on Trotterization but difficult due to the complex
structure of the Trotter error. Here we develop a method measuring the Trotter
error by combining the second- and fourth-order Trotterizations rather than
consulting with mathematical error bounds. Implementing this method, we
construct an algorithm, which we name Trotter24, for adaptively using almost
the largest stepsize , which keeps quantum circuits shallowest,
within an error tolerance preset for our purpose. Trotter24 applies
to generic Hamiltonians, including time-dependent ones, and can be generalized
to any orders of Trotterization. Benchmarking it in a quantum spin chain, we
find the adaptively chosen to be about ten times larger than that
inferred from known upper bounds of Trotter errors. Trotter24 allows us to keep
the quantum circuit thus shallower within the error tolerance in exchange for
paying the cost of measurements.Comment: 11 pages, 6 figure
Elastic Instabilities within Antiferromagnetically Ordered Phase in the Orbitally-Frustrated Spinel GeCoO
Ultrasound velocity measurements of the orbitally-frustrated GeCoO
reveal unusual elastic instabilities due to the phonon-spin coupling within the
antiferromagnetic phase. Shear moduli exhibit anomalies arising from the
coupling to short-range ferromagnetic excitations. Diplike anomalies in the
magnetic-field dependence of elastic moduli reveal magnetic-field-induced
orbital order-order transitions. These results strongly suggest the presence of
geometrical orbital frustration which causes novel orbital phenomena within the
antiferromagnetic phase.Comment: 5 pages, 3 figure
Cooperative Step Climbing Using Connected Wheeled Robots and Evaluation of Remote Operability
The present study evaluates the remote operability of step climbing using two connected robots that are teleoperated by individual operators. In general, a teleoperated robot is manipulated by an operator who is viewing moving images from a camera, which is one of the greatest advantages of such a system. However, robot teleoperation is not easy when a teleoperated robot is affected by the force from another robot or object. We constructed a step climbing system using two connected teleoperated robots. A theoretical analysis and the results of simulations clarified the correlations among the robot velocity, the manipulation time of the robots, and the height of the front wheels when climbing a step. The experimental results demonstrate the step climbing ability of the teleoperated robot system
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