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Articles 1  30 of 183
FullText Articles in Physics
Feasibility Of Electric Field Assisted Clogging Reduction In Cold Gas Spraying Nozzle, Hendric Tronsson
Feasibility Of Electric Field Assisted Clogging Reduction In Cold Gas Spraying Nozzle, Hendric Tronsson
ENGS 88 Honors Thesis (AB Students)
The relatively novel cold spraying process expands its range of applications constantly. In order to continue this trend, this process still has various hurdles that need to be overcome such as clogging. Clogging within the cold gas spraying process causes porous coatings with less material properties and lower durability; a solution is needed in order to reduce the clogging and so expand the cold gas spraying applications. This study aimed to explore the feasibility of using an electric field to reduce clogging. To do so a simplified channel was used to simulate charged particle trajectory shifts under the influence of ...
Mermin Inequalities For Perfect Correlations In ManyQutrit Systems, Jay Lawrence
Mermin Inequalities For Perfect Correlations In ManyQutrit Systems, Jay Lawrence
Open Dartmouth: Published works by Dartmouth faculty
The existence of GreenbergerHorneZeilinger (GHZ) contradictions in manyqutrit systems was a longstanding theoretical question until its (affirmative) resolution in 2013. To enable experimental tests, we derive Mermin inequalities from concurrent observable sets identified in those proofs. These employ a weighted sum of observables, called M, in which every term has the chosen GHZ state as an eigenstate with eigenvalue unity. The quantum prediction for M is then just the number of concurrent observables, and this grows asymptotically as 2N/3 as the number of qutrits N→∞. The maximum classical value falls short for every N≥3, so that the quantum ...
Operator Locality In The Quantum Simulation Of Fermionic Models, Vojtěch Havlíček, Matthias Troyer, James D. Whitfield
Operator Locality In The Quantum Simulation Of Fermionic Models, Vojtěch Havlíček, Matthias Troyer, James D. Whitfield
Open Dartmouth: Published works by Dartmouth faculty
Simulating fermionic lattice models with qubits requires mapping fermionic degrees of freedom to qubits. The simplest method for this task, the JordanWigner transformation, yields strings of Pauli operators acting on an extensive number of qubits. This overhead can be a hindrance to implementation of qubitbased quantum simulators, especially in the analog context. Here we thus review and analyze alternative fermiontoqubit mappings, including the two approaches by Bravyi and Kitaev and the Auxiliary Fermion transformation. The BravyiKitaev transform is reformulated in terms of a classical data structure and generalized to achieve a further locality improvement for local fermionic models on a ...
AllOptical Cooling Of Fermi Gases Via Pauli Inhibition Of Spontaneous Emission, Roberto Onofrio
AllOptical Cooling Of Fermi Gases Via Pauli Inhibition Of Spontaneous Emission, Roberto Onofrio
Open Dartmouth: Published works by Dartmouth faculty
A technique is proposed to cool Fermi gases to the regime of quantum degeneracy based on the expected inhibition of spontaneous emission due to the Pauli principle. The reduction of the linewidth for spontaneous emission originates a corresponding reduction of the Doppler temperature, which under specific conditions may give rise to a runaway process through which fermions are progressively cooled. The approach requires a combination of a magnetooptical trap as a cooling system and an optical dipole trap to enhance quantum degeneracy. This results in expected Fermi degeneracy factors T/TF comparable to the lowest values recently achieved, with potential ...
Pattern Phase Transitions Of SelfPropelled Particles: Gases, Crystals, Liquids, And Mills, Zhao Cheng, Zhiyong Chen, Tamás Vicsek, Duxin Chen
Pattern Phase Transitions Of SelfPropelled Particles: Gases, Crystals, Liquids, And Mills, Zhao Cheng, Zhiyong Chen, Tamás Vicsek, Duxin Chen
Open Dartmouth: Published works by Dartmouth faculty
To understand the collective behaviors of biological swarms, flocks, and colonies, we investigated the nonequilibrium dynamic patterns of selfpropelled particle systems using statistical mechanics methods and Hstability analysis of Hamiltonian systems. By varying the individual vision range, we observed phase transitions between four phases, i.e., gas, crystal, liquid, and millliquid coexistence patterns. In addition, by varying the interparticle force, we detected three distinct milling subphases, i.e., ring, annulus, and disk. Based on the coherent analysis for collective motions, one may predict the stability and adjust the morphology of the phases of selfpropelled particles, which has promising potential ...
Local Spin Operators For Fermion Simulations, James D. Whitfield, Vojtěch Havlíček, Matthias Troyer
Local Spin Operators For Fermion Simulations, James D. Whitfield, Vojtěch Havlíček, Matthias Troyer
Open Dartmouth: Published works by Dartmouth faculty
Digital quantum simulation of fermionic systems is important in the context of chemistry and physics. Simulating fermionic models on general purpose quantum computers requires imposing a fermionic algebra on qubits. The previously studied JordanWigner and BravyiKitaev transformations are two techniques for accomplishing this task. Here, we reexamine an auxiliary fermion construction which maps fermionic operators to local operators on qubits. The local simulation is performed by relaxing the requirement that the number of qubits should match the number of singleparticle states. Instead, auxiliary sites are introduced to enable nonconsecutive fermionic couplings to be simulated with constant lowrank tensor products on ...
Discrimination Between SpinDependent Charge Transport And SpinDependent Recombination In ΠConjugated Polymers By Correlated Current And ElectroluminescenceDetected Magnetic Resonance, Marzieh Kavand, Douglas Baird, Kipp Van Schooten, Hans Malissa
Discrimination Between SpinDependent Charge Transport And SpinDependent Recombination In ΠConjugated Polymers By Correlated Current And ElectroluminescenceDetected Magnetic Resonance, Marzieh Kavand, Douglas Baird, Kipp Van Schooten, Hans Malissa
Open Dartmouth: Published works by Dartmouth faculty
Spindependent processes play a crucial role in organic electronic devices. Spin coherence can give rise to spin mixing due to a number of processes such as hyperfine coupling, and leads to a range of magnetic field effects. However, it is not straightforward to differentiate between pure singlecarrier spindependent transport processes which control the current and therefore the electroluminescence, and spindependent electronhole recombination which determines the electroluminescence yield and in turn modulates the current. We therefore investigate the correlation between the dynamics of spindependent electric current and spindependent electroluminescence in two derivatives of the conjugated polymer poly(phenylenevinylene) using simultaneously measured ...
Exact Solution Of Quadratic Fermionic Hamiltonians For Arbitrary Boundary Conditions, Abhijeet Alase, Emilio Cobanera, Gerardo Ortiz, Lorenza Viola
Exact Solution Of Quadratic Fermionic Hamiltonians For Arbitrary Boundary Conditions, Abhijeet Alase, Emilio Cobanera, Gerardo Ortiz, Lorenza Viola
Open Dartmouth: Published works by Dartmouth faculty
We present a procedure for exactly diagonalizing finiterange quadratic fermionic Hamiltonians with arbitrary boundary conditions in one of D dimensions, and periodic in the remaining D−1. The key is a Hamiltoniandependent separation of the bulk from the boundary. By combining information from the two, we identify a matrix function that fully characterizes the solutions, and may be used to construct an efficiently computable indicator of bulkboundary correspondence. As an illustration, we show how our approach correctly describes the zeroenergy Majorana modes of a timereversalinvariant swave twoband superconductor in a Josephson ring configuration, and predicts that a fractional 4πperiodic Josephson ...
Inflation And The Quantum Measurement Problem, Stephon Alexander, Dhrubo Jyoti, João Magueijo
Inflation And The Quantum Measurement Problem, Stephon Alexander, Dhrubo Jyoti, João Magueijo
Open Dartmouth: Published works by Dartmouth faculty
We propose a solution to the quantum measurement problem in inflation. Our model treats Fourier modes of cosmological perturbations as analogous to particles in a weakly interacting Bose gas. We generalize the idea of a macroscopic wave function to cosmological fields, and construct a selfinteraction Hamiltonian that focuses that wave function. By appropriately setting the coupling between modes, we obtain the standard adiabatic, scaleinvariant power spectrum. Because of central limit theorem, we recover a Gaussian random field, consistent with observations.
A Proposal On Culling & Filtering A Coxeter Group For 4d, N = 1 Spacetime Susy Representations: Revised, D. E. A. Gates, S. James Gates, Kory Stiffler
A Proposal On Culling & Filtering A Coxeter Group For 4d, N = 1 Spacetime Susy Representations: Revised, D. E. A. Gates, S. James Gates, Kory Stiffler
Open Dartmouth: Published works by Dartmouth faculty
We present an expanded and detailed discussion of the mathematical tools required to cull and filter representations of the Coxeter Group BC 4 into providing bases for the construction of minimal offshell representations of the 4D, N" role="presentation" style="boxsizing: borderbox; display: inlinetable; lineheight: normal; letterspacing: normal; wordspacing: normal; wordwrap: normal; whitespace: nowrap; float: none; direction: ltr; maxwidth: none; maxheight: none; minwidth: 0px; minheight: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">NN = 1 spacetime supersymmetry algebra.
Dynamical Decoupling Sequences For MultiQubit Dephasing Suppression And LongTime Quantum Memory, Gerardo A. PazSilva, SeungWoo Lee, Todd J. Green, Lorenza Viola
Dynamical Decoupling Sequences For MultiQubit Dephasing Suppression And LongTime Quantum Memory, Gerardo A. PazSilva, SeungWoo Lee, Todd J. Green, Lorenza Viola
Open Dartmouth: Published works by Dartmouth faculty
We consider a class of multiqubit dephasing models that combine classical noise sources and linear coupling to a bosonic environment, and are controlled by arbitrary sequences of dynamical decoupling pulses. Building on a general transfer filterfunction framework for openloop control, we provide an exact representation of the controlled dynamics for arbitrary stationary nonGaussian classical and quantum noise statistics, with analytical expressions emerging when all dephasing sources are Gaussian. This exact characterization is used to establish two main results. First, we construct multiqubit sequences that ensure maximum highorder error suppression in both the time and frequency domain and that can be ...
Superadiabatic Control Of Quantum Operations, Jonathan Vandermause, Chandrasekhar Ramanathan
Superadiabatic Control Of Quantum Operations, Jonathan Vandermause, Chandrasekhar Ramanathan
Open Dartmouth: Published works by Dartmouth faculty
Adiabatic pulses are used extensively to enable robust control of quantum operations. We introduce an approach to adiabatic control that uses the superadiabatic quality factor as a performance metric to design robust, highfidelity pulses. This approach permits the systematic design of quantum control schemes to maximize the adiabaticity of a unitary operation in a particular time interval given the available control resources. The interplay between adiabaticity, fidelity, and robustness of the resulting pulses is examined for the case of singlequbit inversion, and superadiabatic pulses are demonstrated to have improved robustness to control errors. A numerical search strategy is developed to ...
Effective Microscopic Models For Sympathetic Cooling Of Atomic Gases, Roberto Onofrio, Bala Sundaram
Effective Microscopic Models For Sympathetic Cooling Of Atomic Gases, Roberto Onofrio, Bala Sundaram
Open Dartmouth: Published works by Dartmouth faculty
Thermalization of a system in the presence of a heat bath has been the subject of many theoretical investigations especially in the framework of solidstate physics. In this setting, the presence of a large bandwidth for the frequency distribution of the harmonic oscillators schematizing the heat bath is crucial, as emphasized in the CaldeiraLeggett model. By contrast, ultracold gases in atomic traps oscillate at welldefined frequencies and therefore seem to lie outside the CaldeiraLeggett paradigm. We introduce interaction Hamiltonians which allow us to adapt the model to an atomic physics framework. The intrinsic nonlinearity of these models differentiates them from ...
Magnetohydrodynamic Modeling Of Three Van Allen Probes Storms In 2012 And 2013, J. Paral, M. K. Hudson, B. T. Kress, M. J. Wiltberger
Magnetohydrodynamic Modeling Of Three Van Allen Probes Storms In 2012 And 2013, J. Paral, M. K. Hudson, B. T. Kress, M. J. Wiltberger
Open Dartmouth: Published works by Dartmouth faculty
Coronal mass ejection (CME)shock compression of the dayside magnetopause has been observed to cause both prompt enhancement of radiation belt electron flux due to inward radial transport of electrons conserving their first adiabatic invariant and prompt losses which at times entirely eliminate the outer zone. Recent numerical studies suggest that enhanced ultralow frequency (ULF) wave activity is necessary to explain electron losses deeper inside the magnetosphere than magnetopause incursion following CMEshock arrival. A combination of radial transport and magnetopause shadowing can account for losses observed at radial distances into L=4.5, well within the computed magnetopause location. We ...
Higgs Shifts From Electron–Positron Annihilations Near Neutron Stars, Gary A. Wegner, Roberto Onofrio
Higgs Shifts From Electron–Positron Annihilations Near Neutron Stars, Gary A. Wegner, Roberto Onofrio
Open Dartmouth: Published works by Dartmouth faculty
We discuss the potential for using neutron stars to determine bounds on the HiggsKretschmann coupling by looking at peculiar shifts in gammaray spectroscopic features. In particular, we reanalyze multiple lines observed in GRB781119 detected by two gammaray spectrometers, and derive an upper bound on the HiggsKretschmann coupling that is much more constraining than the one recently obtained from white dwarfs. This calls for targeted analyses of spectra of gammaray bursts from more recent observatories, dedicated searches for differential shifts on electron–positron and proton–antiproton annihilation spectra in proximity of compact sources, and signals of electron and proton cyclotron lines ...
Gps Phase Scintillation At High Latitudes During Geomagnetic Storms Of 7–17 March 2012 – Part 1: The North American Sector, P. Prikryl, R. GhoddousiFard, E. G. Thomas, J. M. Ruohoniemi, S. G. Shepherd
Gps Phase Scintillation At High Latitudes During Geomagnetic Storms Of 7–17 March 2012 – Part 1: The North American Sector, P. Prikryl, R. GhoddousiFard, E. G. Thomas, J. M. Ruohoniemi, S. G. Shepherd
Open Dartmouth: Published works by Dartmouth faculty
During the ascending phase of solar cycle 24, a series of interplanetary coronal mass ejections (ICMEs) in the period 7–17 March 2012 caused geomagnetic storms that strongly affected highlatitude ionosphere in the Northern and Southern Hemisphere. GPS phase scintillation was observed at northern and southern high latitudes by arrays of GPS ionospheric scintillation and TEC monitors (GISTMs) and geodeticquality GPS receivers sampling at 1 Hz. Mapped as a function of magnetic latitude and magnetic local time, regions of enhanced scintillation are identified in the context of coupling processes between the solar wind and the magnetosphere–ionosphere system. Large southward ...
Dynamical Generation Of Floquet Majorana Flat Bands In SWave Superconductors, A. Poudel, G. Ortiz, L. Viola
Dynamical Generation Of Floquet Majorana Flat Bands In SWave Superconductors, A. Poudel, G. Ortiz, L. Viola
Open Dartmouth: Published works by Dartmouth faculty
We present quantum control techniques to engineer flat bands of symmetryprotected Majorana edge modes in s wave superconductors. Specifically, we show how periodic control may be employed for designing timeindependent effective Hamiltonians, which support Floquet Majorana flat bands, starting from equilibrium conditions that are either topologically trivial or only support individual Majorana pairs. In the first approach, a suitable modulation of the chemical potential simultaneously induces Majorana flat bands and dynamically activates a preexisting chiral symmetry which is responsible for their protection. In the second approach, the application of effective parity kicks dynamically generates a desired chiral symmetry by suppressing ...
GravitationalWave Mediated Preheating, Stephon Alexander, Sam Cormack, Antonino Marcianò, Nicolás Yunes
GravitationalWave Mediated Preheating, Stephon Alexander, Sam Cormack, Antonino Marcianò, Nicolás Yunes
Open Dartmouth: Published works by Dartmouth faculty
We propose a new preheating mechanism through the coupling of the gravitational field to both the inflaton and matter fields, without direct inflaton–matter couplings. The inflaton transfers power to the matter fields through interactions with gravitational waves, which are exponentially enhanced due to an inflation–graviton coupling. One such coupling is the product of the inflaton to the Pontryagin density, as in dynamical Chern–Simons gravity. The energy scales involved are constrained by requiring that preheating happens fast during matter domination.
Switching Quantum Dynamics For Fast Stabilization, Pierre Scaramuzza, Francesco Ticozzi
Switching Quantum Dynamics For Fast Stabilization, Pierre Scaramuzza, Francesco Ticozzi
Open Dartmouth: Published works by Dartmouth faculty
Control strategies for dissipative preparation of target quantum states, both pure and mixed, and subspaces are obtained by switching between a set of available semigroup generators. We show that the class of problems of interest can be recast, from a controltheoretic perspective, into a switchedstabilization problem for linear dynamics. This is attained by a suitable affine transformation of the coherencevector representation. In particular, we propose and compare stabilizing timebased and statebased switching rules for entangled state preparation, showing that the latter not only ensure faster convergence with respect to nonswitching methods, but can be designed so that they retain robustness ...
DualSpacecraft Reconstruction Of A ThreeDimensional Magnetic Flux Rope At The Earth's Magnetopause, H. Hasegawa, B. U. Ö. Sonnerup, S. Eriksson, T. K. M. Nakamura
DualSpacecraft Reconstruction Of A ThreeDimensional Magnetic Flux Rope At The Earth's Magnetopause, H. Hasegawa, B. U. Ö. Sonnerup, S. Eriksson, T. K. M. Nakamura
Open Dartmouth: Published works by Dartmouth faculty
We present the first results of a data analysis method, developed by Sonnerup and Hasegawa (2011), for reconstructing threedimensional (3D), magnetohydrostatic structures from data taken as two closely spaced satellites traverse the structures. The method is applied to a magnetic flux transfer event (FTE), which was encountered on 27 June 2007 by at least three (THC, THD, and THE) of the five THEMIS probes near the subsolar magnetopause. The FTE was sandwiched between two oppositely directed reconnection jets under a southward interplanetary magnetic field condition, consistent with its generation by multiple Xline reconnection. The recovered 3D field indicates that a ...
Maximally Entangled States Of Four Nnonbinary Particles, Mario Gaeta, Andrei Klimov, Jay Lawrence
Maximally Entangled States Of Four Nnonbinary Particles, Mario Gaeta, Andrei Klimov, Jay Lawrence
Open Dartmouth: Published works by Dartmouth faculty
Systems of four nonbinary particles, with each particle having d≥3 internal states, exhibit maximally entangled states that are inaccessible to four qubits. This breaks the pattern of two and threeparticle systems, in which the existing graph states are equally accessible to binary and nonbinary systems alike. We compare the entanglement properties of these special states (called P states) with those of the more familiar GreenbergerHorneZeilinger (GHZ) and cluster states accessible to qubits. The comparison includes familiar entanglement measures, the “steering” of states by projective measurements, and the probability that two such measurements, chosen at random, leave the remaining particles ...
Robust Fast Direct Integral Equation Solver For QuasiPeriodic Scattering Problems With A Large Number Of Layers, Min Hyung Cho, Alex H. Barnett
Robust Fast Direct Integral Equation Solver For QuasiPeriodic Scattering Problems With A Large Number Of Layers, Min Hyung Cho, Alex H. Barnett
Open Dartmouth: Published works by Dartmouth faculty
We present a new boundary integral formulation for timeharmonic wave diffraction from twodimensional structures with many layers of arbitrary periodic shape, such as multilayer dielectric gratings in TM polarization. Our scheme is robust at all scattering parameters, unlike the conventional quasiperiodic Green’s function method which fails whenever any of the layers approaches a Wood anomaly. We achieve this by a decomposition into near and farfield contributions. The former uses the freespace Green’s function in a secondkind integral equation on one period of the material interfaces and their immediate left and right neighbors; the latter uses proxy point sources ...
Inductive Measurement Of Optically Hyperpolarized Phosphorous Donor Nuclei In An Isotopically Enriched Silicon28 Crystal, P. Gumann, O. Patange, C. Ramanathan, H. Haas
Inductive Measurement Of Optically Hyperpolarized Phosphorous Donor Nuclei In An Isotopically Enriched Silicon28 Crystal, P. Gumann, O. Patange, C. Ramanathan, H. Haas
Open Dartmouth: Published works by Dartmouth faculty
We experimentally demonstrate the first inductive readout of optically hyperpolarized phosphorus31 donor nuclear spins in an isotopically enriched silicon28 crystal. The concentration of phosphorus donors in the crystal was 1.5×1015 cm−3, 3 orders of magnitude lower than has previously been detected via direct inductive detection. The signaltonoise ratio measured in a single free induction decay from a 1 cm3 sample (≈1015 spins) was 113. By transferring the sample to an Xband ESR spectrometer, we were able to obtain a lower bound for the nuclear spin polarization at 1.7 K of ∼64%. The 31PT2 measured with a ...
Iterative Solutions To The SteadyState Density Matrix For Optomechanical Systems, P. D. Nation, J. R. Johansson, M. P. Blencowe, A. J. Rimberg
Iterative Solutions To The SteadyState Density Matrix For Optomechanical Systems, P. D. Nation, J. R. Johansson, M. P. Blencowe, A. J. Rimberg
Open Dartmouth: Published works by Dartmouth faculty
We present a sparse matrix permutation from graph theory that gives stable incomplete Lower Upper (LU) preconditioners necessary for iterative solutions to the steady state density matrix for quantum optomechanical systems. This reordering is efficient, adding little overhead to the computation, and results in a marked reduction in both memory and runtime requirements compared to other solution methods, with performance gains increasing with system size. Either of these benchmarks can be tuned via the preconditioner accuracy and solution tolerance. This reordering optimizes the condition number of the approximate inverse, and is the only method found to be stable at large ...
InformationEntropic Measure Of EnergyDegenerate Kinks In TwoField Models, R.A.C. Correa, A. De Souza Dutra, M. Gleiser
InformationEntropic Measure Of EnergyDegenerate Kinks In TwoField Models, R.A.C. Correa, A. De Souza Dutra, M. Gleiser
Open Dartmouth: Published works by Dartmouth faculty
We investigate the existence and properties of kinklike solitons in a class of models with two interacting scalar fields. In particular, we focus on models that display both double and singlekink solutions, treatable analytically using the Bogomol'nyi–Prasad–Sommerfield bound (BPS). Such models are of interest in applications that include Skyrmions and various superstringmotivated theories. Exploring a region of parameter space where the energy for very different spatiallybound configurations is degenerate, we show that a newlyproposed momentum–space entropic measure called Configurational Entropy (CE) can distinguish between such energydegenerate spatial profiles. This informationtheoretic measure of spatial complexity provides a ...
General TransferFunction Approach To Noise Filtering In OpenLoop Quantum Control, Gerardo A. PazSilva, Lorenza Viola
General TransferFunction Approach To Noise Filtering In OpenLoop Quantum Control, Gerardo A. PazSilva, Lorenza Viola
Open Dartmouth: Published works by Dartmouth faculty
We present a general transferfunction approach to noise filtering in openloop Hamiltonian engineering protocols for open quantum systems. We show how to identify a computationally tractable set of fundamental filter functions, out of which arbitrary transfer filter functions may be assembled up to arbitrary high order in principle. Besides avoiding the infinite recursive hierarchy of filter functions that arises in general control scenarios, this fundamental filterfunctions set suffices to characterize the error suppression capabilities of the control protocol in both the time and frequency domain. We prove that the resulting notion of filtering order reveals conceptually distinct, albeit complementary, features ...
Robustness Of Composite Pulses To TimeDependent Control Noise, Chingiz Kabytayev, Todd J. Green, Kaveh Khodjasteh, Michael J. Biercuk, Lorenza Viola, Kenneth R. Brown
Robustness Of Composite Pulses To TimeDependent Control Noise, Chingiz Kabytayev, Todd J. Green, Kaveh Khodjasteh, Michael J. Biercuk, Lorenza Viola, Kenneth R. Brown
Open Dartmouth: Published works by Dartmouth faculty
We study the performance of composite pulses in the presence of timevarying control noise on a single qubit. These protocols, originally devised only to correct for static, systematic errors, are shown to be robust to timedependent nonMarkovian noise in the control field up to frequencies as high as ∼10% of the Rabi frequency. Our study combines a generalized filterfunction approach with asymptotic dclimit calculations to give a simple analytic framework for error analysis applied to a number of compositepulse sequences relevant to nuclear magnetic resonance as well as quantum information experiments. Results include examination of recently introduced concatenated composite pulses ...
Fundamental Bounds In Measurements For Estimating Quantum States, HyangTag Lim, YoungSik Ra, KangHee Hong, SeungWoo Lee, YoonHo Kim
Fundamental Bounds In Measurements For Estimating Quantum States, HyangTag Lim, YoungSik Ra, KangHee Hong, SeungWoo Lee, YoonHo Kim
Open Dartmouth: Published works by Dartmouth faculty
Quantum measurement unavoidably disturbs the state of a quantum system if any information about the system is extracted. Recently, the concept of reversing quantum measurement has been introduced and has attracted much attention. Numerous efforts have thus been devoted to understanding the fundamental relation of the amount of information obtained by measurement to either state disturbance or reversibility. Here, we experimentally prove the tradeoff relations in quantum measurement with respect to both state disturbance and reversibility. By demonstrating the quantitative bound of the tradeoff relations, we realize an optimal measurement for estimating quantum systems with minimum disturbance and maximum reversibility ...
Signatures Of The Valley Kondo Effect In Si/Sige Quantum Dots, Mingyun Yuan, R. Joynt, Zhen Yang, Chunyang Tang, D. E. Savage, M. G. Lagally, M. A. Eriksson, A. J. Rimberg
Signatures Of The Valley Kondo Effect In Si/Sige Quantum Dots, Mingyun Yuan, R. Joynt, Zhen Yang, Chunyang Tang, D. E. Savage, M. G. Lagally, M. A. Eriksson, A. J. Rimberg
Open Dartmouth: Published works by Dartmouth faculty
We report measurements consistent with the valley Kondo effect in Si/SiGe quantum dots, evidenced by peaks in the conductance versus sourcedrain voltage that show strong temperature dependence. The Kondo peaks show unusual behavior in a magnetic field that we interpret as arising from the valley degree of freedom. The interplay of valley and Zeeman splittings is suggested by the presence of side peaks, revealing a zerofield valley splitting between 0.28 to 0.34 meV. A zerobias conductance peak for nonzero magnetic field, a phenomenon consistent with valley nonconservation in tunneling, is observed in two samples.
Quantum Resources For Purification And Cooling: Fundamental Limits And Opportunities, Francesco Ticozzi, Lorenza Viola
Quantum Resources For Purification And Cooling: Fundamental Limits And Opportunities, Francesco Ticozzi, Lorenza Viola
Open Dartmouth: Published works by Dartmouth faculty
Preparing a quantum system in a pure state is ultimately limited by the nature of the system's evolution in the presence of its environment and by the initial state of the environment itself. We show that, when the system and environment are initially uncorrelated and arbitrary joint unitary dynamics is allowed, the system may be purified up to a certain (possibly arbitrarily small) threshold if and only if its environment, either natural or engineered, contains a “virtual subsystem” which has the same dimension and is in a state with the desired purity. Beside providing a unified understanding of quantum ...