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Full-Text Articles in Physical Sciences and Mathematics
Mermin Inequalities For Perfect Correlations In Many-Qutrit Systems, Jay Lawrence
Mermin Inequalities For Perfect Correlations In Many-Qutrit Systems, Jay Lawrence
Dartmouth Scholarship
The existence of Greenberger-Horne-Zeilinger (GHZ) contradictions in many-qutrit systems was a long-standing 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 to classical …
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
Dartmouth Scholarship
Simulating fermionic lattice models with qubits requires mapping fermionic degrees of freedom to qubits. The simplest method for this task, the Jordan-Wigner transformation, yields strings of Pauli operators acting on an extensive number of qubits. This overhead can be a hindrance to implementation of qubit-based quantum simulators, especially in the analog context. Here we thus review and analyze alternative fermion-to-qubit mappings, including the two approaches by Bravyi and Kitaev and the Auxiliary Fermion transformation. The Bravyi-Kitaev transform is reformulated in terms of a classical data structure and generalized to achieve a further locality improvement for local fermionic models on a …
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
Dartmouth Scholarship
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 Jordan-Wigner and Bravyi-Kitaev 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 single-particle states. Instead, auxiliary sites are introduced to enable nonconsecutive fermionic couplings to be simulated with constant low-rank tensor products on …
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
Dartmouth Scholarship
We present a procedure for exactly diagonalizing finite-range quadratic fermionic Hamiltonians with arbitrary boundary conditions in one of D dimensions, and periodic in the remaining D−1. The key is a Hamiltonian-dependent 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 bulk-boundary correspondence. As an illustration, we show how our approach correctly describes the zero-energy Majorana modes of a time-reversal-invariant s-wave two-band superconductor in a Josephson ring configuration, and predicts that a fractional 4π-periodic Josephson effect …
Dynamical Decoupling Sequences For Multi-Qubit Dephasing Suppression And Long-Time Quantum Memory, Gerardo A. Paz-Silva, Seung-Woo Lee, Todd J. Green, Lorenza Viola
Dynamical Decoupling Sequences For Multi-Qubit Dephasing Suppression And Long-Time Quantum Memory, Gerardo A. Paz-Silva, Seung-Woo Lee, Todd J. Green, Lorenza Viola
Dartmouth Scholarship
We consider a class of multi-qubit 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 filter-function framework for open-loop control, we provide an exact representation of the controlled dynamics for arbitrary stationary non-Gaussian 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 multi-qubit sequences that ensure maximum high-order error suppression in both the time and frequency domain and that can be …
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
Dartmouth Scholarship
Thermalization of a system in the presence of a heat bath has been the subject of many theoretical investigations especially in the framework of solid-state 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 Caldeira-Leggett model. By contrast, ultracold gases in atomic traps oscillate at well-defined frequencies and therefore seem to lie outside the Caldeira-Leggett 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 …
Switching Quantum Dynamics For Fast Stabilization, Pierre Scaramuzza, Francesco Ticozzi
Switching Quantum Dynamics For Fast Stabilization, Pierre Scaramuzza, Francesco Ticozzi
Dartmouth Scholarship
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 control-theoretic perspective, into a switched-stabilization problem for linear dynamics. This is attained by a suitable affine transformation of the coherence-vector representation. In particular, we propose and compare stabilizing time-based and state-based 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 …
General Transfer-Function Approach To Noise Filtering In Open-Loop Quantum Control, Gerardo A. Paz-Silva, Lorenza Viola
General Transfer-Function Approach To Noise Filtering In Open-Loop Quantum Control, Gerardo A. Paz-Silva, Lorenza Viola
Dartmouth Scholarship
We present a general transfer-function approach to noise filtering in open-loop 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 filter-functions 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, …
Robustness Of Composite Pulses To Time-Dependent Control Noise, Chingiz Kabytayev, Todd J. Green, Kaveh Khodjasteh, Michael J. Biercuk, Lorenza Viola, Kenneth R. Brown
Robustness Of Composite Pulses To Time-Dependent Control Noise, Chingiz Kabytayev, Todd J. Green, Kaveh Khodjasteh, Michael J. Biercuk, Lorenza Viola, Kenneth R. Brown
Dartmouth Scholarship
We study the performance of composite pulses in the presence of time-varying control noise on a single qubit. These protocols, originally devised only to correct for static, systematic errors, are shown to be robust to time-dependent non-Markovian noise in the control field up to frequencies as high as ∼10% of the Rabi frequency. Our study combines a generalized filter-function approach with asymptotic dc-limit calculations to give a simple analytic framework for error analysis applied to a number of composite-pulse sequences relevant to nuclear magnetic resonance as well as quantum information experiments. Results include examination of recently introduced concatenated composite pulses …
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
Dartmouth Scholarship
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 purification …
Exact And Approximate Solutions For The Quantum Minimum-Kullback-Entropy Estimation Problem, Carlo Sparaciari, Stefano Olivares, Francesco Ticozzi, Matteo G. A. Paris
Exact And Approximate Solutions For The Quantum Minimum-Kullback-Entropy Estimation Problem, Carlo Sparaciari, Stefano Olivares, Francesco Ticozzi, Matteo G. A. Paris
Dartmouth Scholarship
The minimum-Kullback-entropy principle (mKE) is a useful tool to estimate quantum states and operations from incomplete data and prior information. In general, the solution of an mKE problem is analytically challenging and an approximate solution has been proposed and employed in different contexts. Recently, the form and a way to compute the exact solution for finite dimensional systems has been found, and a question naturally arises on whether the approximate solution could be an effective substitute for the exact solution, and in which regimes this substitution can be performed. Here, we provide a systematic comparison between the exact and the …
Majorana Flat Bands In S -Wave Gapless Topological Superconductors, Shusa Deng, Gerardo Ortiz, Amrit Poudel, Lorenza Viola
Majorana Flat Bands In S -Wave Gapless Topological Superconductors, Shusa Deng, Gerardo Ortiz, Amrit Poudel, Lorenza Viola
Dartmouth Scholarship
We demonstrate how the nontrivial interplay between spin-orbit coupling and nodeless s-wave superconductivity can drive a fully gapped two-band topological insulator into a time-reversal invariant gapless topological superconductor supporting symmetry-protected Majorana flat bands. We characterize topological phase diagrams by a Z2×Z2 partial Berry-phase invariant, and show that, despite the trivial crystal geometry, no unique bulk-boundary correspondence exists. We trace this behavior to the anisotropic quasiparticle bulk gap closing, linear vs quadratic, and argue that this provides a unifying principle for gapless topological superconductivity. Experimental implications for tunneling conductance measurements are addressed, relevant for lead chalcogenide materials.
Asymmetric Architecture For Heralded Single-Photon Sources, Luca Mazzarella, Francesco Ticozzi, Alexander V. Sergienko, Giuseppe Vallone, Paolo Villoresi
Asymmetric Architecture For Heralded Single-Photon Sources, Luca Mazzarella, Francesco Ticozzi, Alexander V. Sergienko, Giuseppe Vallone, Paolo Villoresi
Dartmouth Scholarship
Single-photon sources represent a fundamental building block for optical implementations of quantum information tasks ranging from basic tests of quantum physics to quantum communication and high-resolution quantum measurement. In this paper, in order to compare the effectiveness of different designs, we introduce a single-photon source performance index, based on the maximum probability of generating a single photon that still guarantees a given signal-to-noise ratio. We then investigate the performance of a multiplexed system based on asymmetric configuration of multiple heralded single-photon sources. The performance and scalability comparison with both currently existing multiple-source architectures and faint laser configurations reveals an advantage …
Multiband S -Wave Topological Superconductors: Role Of Dimensionality And Magnetic Field Response, Shusa Deng, Gerardo Ortiz, Lorenza Viola
Multiband S -Wave Topological Superconductors: Role Of Dimensionality And Magnetic Field Response, Shusa Deng, Gerardo Ortiz, Lorenza Viola
Dartmouth Scholarship
We further investigate a class of time-reversal-invariant two-band s-wave topological superconductors introduced earlier [Deng, Viola, and Ortiz, Phys. Rev. Lett. 108, 036803 (2012)]. Provided that a sign reversal between the two superconducting pairing gaps is realized, the topological phase diagram can be determined exactly (within mean field) in one and two dimensions as well as in three dimensions upon restricting to the excitation spectrum of time-reversal-invariant momentum modes. We show how, in the presence of time-reversal symmetry, Z2 invariants that distinguish between trivial and nontrivial quantum phases can be constructed by considering only one of the Kramers’ sectors …
Automated Synthesis Of Dynamically Corrected Quantum Gates, Kaveh Khodjasteh, Hendrik Bluhm, Lorenza Viola
Automated Synthesis Of Dynamically Corrected Quantum Gates, Kaveh Khodjasteh, Hendrik Bluhm, Lorenza Viola
Dartmouth Scholarship
Dynamically corrected gates are extended to non-Markovian open quantum systems where limitations on the available controls and/or the presence of control noise make existing analytical approaches unfeasible. A computational framework for the synthesis of dynamically corrected gates is formalized that allows sensitivity against non-Markovian decoherence and control errors to be perturbatively minimized via numerical search, resulting in robust gate implementations. Explicit sequences for achieving universal high-fidelity control in a singlet-triplet spin qubit subject to realistic system and control constraint are provided, which simultaneously cancel to the leading order the dephasing due to non-Markovian nuclear-bath dynamics and voltage noise affecting the …
Nanomechanical Resonator Coupled Linearly Via Its Momentum To A Quantum Point Contact, Latchezar L. Benatov, Miles P. Blencowe
Nanomechanical Resonator Coupled Linearly Via Its Momentum To A Quantum Point Contact, Latchezar L. Benatov, Miles P. Blencowe
Dartmouth Scholarship
We use a Born-Markov approximated master equation approach to study the symmetrized-in-frequency current noise spectrum and the oscillator steady state of a nanoelectromechanical system where a nanoscale resonator is coupled linearly via its momentum to a quantum point contact (QPC). Our current noise spectra exhibit clear signatures of the quantum correlations between the QPC current and the back-action force on the oscillator at a value of the relative tunneling phase (η=−π/2) where such correlations are expected to be maximized. We also show that the steady state of the oscillator obeys a classical Fokker-Planck equation, but can experience thermomechanical noise squeezing …
Majorana Modes In Time-Reversal Invariant S -Wave Topological Superconductors, Shusa Deng, Lorenza Viola, Gerardo Ortiz
Majorana Modes In Time-Reversal Invariant S -Wave Topological Superconductors, Shusa Deng, Lorenza Viola, Gerardo Ortiz
Dartmouth Scholarship
We present a time-reversal invariant s-wave superconductor supporting Majorana edge modes. The multiband character of the model together with spin-orbit coupling are key to realizing such a topological superconductor. We characterize the topological phase diagram by using a partial Chern number sum, and show that the latter is physically related to the parity of the fermion number of the time-reversal invariant modes. By taking the self-consistency constraint on the s-wave pairing gap into account, we also establish the possibility of a direct topological superconductor-to-topological insulator quantum phase transition.
Experimental Characterization Of Coherent Magnetization Transport In A One-Dimensional Spin System, Chandrasekhar Ramanathan, Paola Cappellaro, Lorenza Viola, David G. Cory
Experimental Characterization Of Coherent Magnetization Transport In A One-Dimensional Spin System, Chandrasekhar Ramanathan, Paola Cappellaro, Lorenza Viola, David G. Cory
Dartmouth Scholarship
We experimentally characterize the non-equilibrium, room-temperature magnetization dynamics of a spin chain evolving under an effective double-quantum (DQ) Hamiltonian. We show that the Liouville space operators corresponding to the magnetization and the two-spin correlations evolve 90 degrees out of phase with each other, and drive the transport dynamics. For a nearest-neighbor-coupled N-spin chain, the dynamics are found to be restricted to a Liouville operator space whose dimension scales only as N2, leading to a slow growth of multi-spin correlations. Even though long-range couplings are present in the real system, we find excellent agreement between the analytical predictions …
Dynamical Critical Scaling And Effective Thermalization In Quantum Quenches: Role Of The Initial State, Shusa Deng, Gerardo Ortiz, Lorenza Viola
Dynamical Critical Scaling And Effective Thermalization In Quantum Quenches: Role Of The Initial State, Shusa Deng, Gerardo Ortiz, Lorenza Viola
Dartmouth Scholarship
We explore the robustness of universal dynamical scaling behavior in a quantum system near criticality with respect to initialization in a large class of states with finite energy. By focusing on a homogeneous XY quantum spin chain in a transverse field, we characterize the nonequilibrium response under adiabatic and sudden quench processes originating from a pure as well as a mixed excited initial state, and involving either a regular quantum critical or a multicritical point. We find that the critical exponents of the ground-state quantum phase transition can be encoded in the dynamical scaling exponents despite the finite energy of …
The Trilinear Hamiltonian: A Zero-Dimensional Model Of Hawking Radiation From A Quantized Source, Paul D. Nation, Miles P. Blencowe
The Trilinear Hamiltonian: A Zero-Dimensional Model Of Hawking Radiation From A Quantized Source, Paul D. Nation, Miles P. Blencowe
Dartmouth Scholarship
We investigate a quantum parametric amplifier with dynamical pump mode, viewed as a zero-dimensional model of Hawking radiation from an evaporating black hole. We derive the conditions under which the spectrum of particles generated from vacuum fluctuations deviates from the thermal spectrum predicted for the conventional parametric amplifier. We find that significant deviations arise when the pump mode (black hole) has emitted nearly half of its initial energy into the signal (Hawking radiation) and idler (in-falling particle) modes. As a model of black hole dynamics, this finding lends support to the view that late-time Hawking radiation contains information about the …
Equilibrium States Of A Test Particle Coupled To Finite-Size Heat Baths, Qun Wei, S. Taylor Smith, Roberto Onofrio
Equilibrium States Of A Test Particle Coupled To Finite-Size Heat Baths, Qun Wei, S. Taylor Smith, Roberto Onofrio
Dartmouth Scholarship
We report on numerical simulations of the dynamics of a test particle coupled to competing Boltzmann heat baths of finite size. After discussing some features of the single bath case, we show that the presence of two heat baths further constrains the conditions necessary for the test particle to thermalize with the heat baths. We find that thermalization is a spectral property in which the oscillators of the bath with frequencies in the range of the test particle characteristic frequency determine its degree of thermalization. We also find an unexpected frequency shift of the test particle response with respect to …
Arbitrarily Accurate Dynamical Control In Open Quantum Systems, Kaveh Khodjasteh, Daniel A. Lidar, Lorenza Viola
Arbitrarily Accurate Dynamical Control In Open Quantum Systems, Kaveh Khodjasteh, Daniel A. Lidar, Lorenza Viola
Dartmouth Scholarship
We show that open-loop dynamical control techniques may be used to synthesize unitary transformations in open quantum systems in such a way that decoherence is perturbatively compensated for to a desired (in principle arbitrarily high) level of accuracy, which depends only on the strength of the relevant errors and the achievable rate of control modulation. Our constructive and fully analytical solution employs concatenated dynamically corrected gates, and is applicable independently of detailed knowledge of the system-environment interactions and environment dynamics. Explicit implications for boosting quantum gate fidelities in realistic scenarios are addressed.
Damping And Decoherence Of A Nanomechanical Resonator Due To A Few Two-Level Systems, Laura G. Remus, Miles P. Blencowe, Yukihiro Tanaka
Damping And Decoherence Of A Nanomechanical Resonator Due To A Few Two-Level Systems, Laura G. Remus, Miles P. Blencowe, Yukihiro Tanaka
Dartmouth Scholarship
We consider a quantum model of a nanomechanical flexing beam resonator interacting with a bath comprising a few damped tunneling two-level systems. In contrast with a resonator interacting bilinearly with an ohmic free oscillator bath (modeling clamping loss, for example), the mechanical resonator damping is amplitude dependent, while the decoherence of quantum superpositions of mechanical position states depends only weakly on their spatial separation.
Dynamical Quantum Error Correction Of Unitary Operations With Bounded Controls, Kaveh Khodjasteh, Lorenza Viola
Dynamical Quantum Error Correction Of Unitary Operations With Bounded Controls, Kaveh Khodjasteh, Lorenza Viola
Dartmouth Scholarship
Dynamically corrected gates were recently introduced [K. Khodjasteh and L. Viola, Phys. Rev. Lett. 102, 080501 (2009)] as a tool to achieve decoherence-protected quantum gates based on open-loop Hamiltonian engineering. Here, we further expand the framework of dynamical quantum error correction, with emphasis on elucidating under what conditions decoherence suppression can be ensured while performing a generic target quantum gate, using only available bounded-strength control resources. Explicit constructions for physically relevant error models are detailed, including arbitrary linear decoherence and pure dephasing on qubits. The effectiveness of dynamically corrected gates in an illustrative non-Markovian spin-bath setting is investigated numerically, …
Dynamically Error-Corrected Gates For Universal Quantum Computation, Kaveh Khodjasteh, Lorenza Viola
Dynamically Error-Corrected Gates For Universal Quantum Computation, Kaveh Khodjasteh, Lorenza Viola
Dartmouth Scholarship
Scalable quantum computation in realistic devices requires that precise control can be implemented efficiently in the presence of decoherence and operational errors. We propose a general constructive procedure for designing robust unitary gates on an open quantum system without encoding or measurement overhead. Our results allow for a low-level err or correction strategy solely based on Hamiltonian engineering using realistic bounded-strength controls and may substantially reduce implementation requirements for fault-tolerant quantum computing architectures.
Dynamical Non-Ergodic Scaling In Continuous Finite-Order Quantum Phase Transitions, S. Deng, G. Ortiz, L. Viola
Dynamical Non-Ergodic Scaling In Continuous Finite-Order Quantum Phase Transitions, S. Deng, G. Ortiz, L. Viola
Dartmouth Scholarship
We investigate the emergence of universal dynamical scaling in quantum critical spin systems adiabatically driven out of equilibrium, with emphasis on quench dynamics which involves non-isolated critical points (i.e., critical regions) and cannot be a priori described through standard scaling arguments nor time-dependent perturbative approaches. Comparing to the case of an isolated quantum critical point, we find that non-equilibrium scaling behavior of a large class of physical observables may still be explained in terms of equilibrium critical exponents. However, the latter are in general non-trivially path-dependent, and detailed knowledge about the time-dependent excitation process becomes essential. In particular, …
Anomalies In Electrostatic Calibrations For The Measurement Of The Casimir Force In A Sphere-Plane Geometry, W. J. Kim, M. Brown-Hayes, D. A.R. Dalvit, J. H. Brownell, R. Onofrio
Anomalies In Electrostatic Calibrations For The Measurement Of The Casimir Force In A Sphere-Plane Geometry, W. J. Kim, M. Brown-Hayes, D. A.R. Dalvit, J. H. Brownell, R. Onofrio
Dartmouth Scholarship
We have performed precision electrostatic calibrations in the sphere-plane geometry, and observed anomalous behavior. Namely, the scaling exponent of the electrostatic signal with distance was found to be smaller than expected on the basis of the pure Coulombian contribution, and the residual potential found to be distance dependent. We argue that these findings affect the accuracy of the electrostatic calibrations and invite reanalysis of previous determinations of the Casimir force.
Parameters Of Pseudorandom Quantum Circuits, Yaakov S. Weinstein, Winton G. Brown, Lorenza Viola
Parameters Of Pseudorandom Quantum Circuits, Yaakov S. Weinstein, Winton G. Brown, Lorenza Viola
Dartmouth Scholarship
Pseudorandom circuits generate quantum states and unitary operators which are approximately distributed according to the unitarily invariant Haar measure. We explore how several design parameters affect the efficiency of pseudorandom circuits, with the goal of identifying relevant tradeoffs and optimizing convergence. The parameters we explore include the choice of single- and two-qubit gates, the topology of the underlying physical qubit architecture, the probabilistic application of two-qubit gates, as well as circuit size, initialization, and the effect of control constraints. Building on the equivalence between pseudorandom circuits and approximate t-designs, a Markov matrix approach is employed to analyze asymptotic convergence properties …
Probing The Quantum Coherence Of A Nanomechanical Resonator Using A Superconducting Qubit: I. Echo Scheme, A. D. Armour, M. P. Blencowe
Probing The Quantum Coherence Of A Nanomechanical Resonator Using A Superconducting Qubit: I. Echo Scheme, A. D. Armour, M. P. Blencowe
Dartmouth Scholarship
We propose a scheme in which the quantum coherence of a nanomechanical resonator can be probed using a superconducting qubit. We consider a mechanical resonator coupled capacitively to a Cooper pair box and assume that the superconducting qubit is tuned to the degeneracy point so that its coherence time is maximized and the electro-mechanical coupling can be approximated by a dispersive Hamiltonian. When the qubit is prepared in a superposition of states, this drives the mechanical resonator progressively into a superposition which in turn leads to apparent decoherence of the qubit. Applying a suitable control pulse to the qubit allows …
Probing The Quantum Coherence Of A Nanomechanical Resonator Using A Superconducting Qubit: Ii. Implementation, M. P. Blencowe, A. D. Armour
Probing The Quantum Coherence Of A Nanomechanical Resonator Using A Superconducting Qubit: Ii. Implementation, M. P. Blencowe, A. D. Armour
Dartmouth Scholarship
We describe a possible implementation of the nanomechanical quantum superposition generation and detection scheme described in the preceding, companion paper (Armour A D and Blencowe M P 2008 New. J. Phys. 10 095004). The implementation is based on the circuit quantum electrodynamics (QED) set-up, with the addition of a mechanical degree of freedom formed out of a suspended, doubly-clamped segment of the superconducting loop of a dc SQUID located directly opposite the centre conductor of a coplanar waveguide (CPW). The relative merits of two SQUID based qubit realizations are addressed, in particular a capacitively coupled charge qubit and inductively coupled …