Eran Ginossar

Dr Eran Ginossar


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20 ATI 02

Academic and research departments

Advanced Technology Institute, Department of Physics.

Biography

Areas of specialism

Mesoscopic physics; Quantum optics and quantum non-equilibrium; Superconducting circuits ; Quantum optimal control; Topological states of matter; Quantum simulation and quantum computing

University roles and responsibilities

  • MPhys Research Year Placements Coordinator

    Research

    Research interests

    My teaching

    Courses I teach on

    Undergraduate

    My publications

    Publications

    Th Mavrogordatos, F Barratt, U Asari, P Szafulski, Eran Ginossar, M Szymanska (2018)Rare quantum metastable states in the strongly dispersive Jaynes-Cummings oscillator, In: Physical Review A97033828 American Physical Society

    We present evidence of metastable rare quantum- uctuation switching for the driven dissipative Jaynes-Cummings (JC) oscillator coupled to a zero-temperature bath in the strongly dispersive regime. We show that single-atom complex amplitude bistability is accompanied by the appearance of a low-amplitude long-lived transient state, hereinafter called `dark state', having a distribution with quasi-Poissonian statistics both for the coupled qubit and cavity mode. We find that the dark state is linked to a spontaneous ipping of the qubit state, detuning the cavity to a low-photon response. The appearance of the dark state is correlated with the participation of the two metastable states in the dispersive bistability, as evidenced by the solution of the Master Equation and single quantum trajectories.

    Matthew Elliott, Jaewoo Joo, Eran Ginossar (2018)Designing Kerr interactions using multiple superconducting qubit types in a single circuit, In: New Journal of Physics20(2)023037 IOP Publishing

    The engineering of Kerr interactions is of great interest for processing quantum information in multipartite quantum systems and for investigating many-body physics in a complex cavity-qubit network. We study how coupling multiple different types of superconducting qubits to the same cavity modes can be used to modify the self- and cross-Kerr effects acting on the cavities and demonstrate that this type of architecture could be of significant benefit for quantum technologies. Using both analytical perturbation theory results and numerical simulations, we first show that coupling two superconducting qubits with opposite anharmonicities to a single cavity enables the effective self-Kerr interaction to be diminished, while retaining the number splitting effect that enables control and measurement of the cavity field. We demonstrate that this reduction of the self-Kerr effect can maintain the fidelity of coherent states and generalised Schrödinger cat states for much longer than typical coherence times in realistic devices. Next, we find that the cross-Kerr interaction between two cavities can be modified by coupling them both to the same pair of qubit devices. When one of the qubits is tunable in frequency, the strength of entangling interactions between the cavities can be varied on demand, forming the basis for logic operations on the two modes. Finally, we discuss the feasibility of producing an array of cavities and qubits where intermediary and on-site qubits can tune the strength of self- and cross-Kerr interactions across the whole system. This architecture could provide a way to engineer interesting many-body Hamiltonians and be a useful platform for quantum simulation in circuit quantum electrodynamics.

    DI Schuster, AP Sears, E Ginossar, L DiCarlo, L Frunzio, JJ Morton, H Wu, GA Briggs, BB Buckley, DD Awschalom (2010)High-cooperativity coupling of electron-spin ensembles to superconducting cavities., In: Phys Rev Lett105(14)140501 American Physical Society

    Electron spins in solids are promising candidates for quantum memories for superconducting qubits because they can have long coherence times, large collective couplings, and many qubits could be encoded into spin waves of a single ensemble. We demonstrate the coupling of electron-spin ensembles to a superconducting transmission-line cavity at strengths greatly exceeding the cavity decay rates and comparable to the spin linewidths. We also perform broadband spectroscopy of ruby (Al₂O₃:Cr(3+)) at millikelvin temperatures and low powers, using an on-chip feedline. In addition, we observe hyperfine structure in diamond P1 centers.

    TK Mavrogordatos, G Tancredi, Matthew Elliott, MJ Peterer, A Patterson, J Rahamim, PJ Leek, Eran Ginossar, MH Szymanska (2017)Simultaneous bistability of qubit and resonator in circuit quantum electrodynamics, In: Physical Review Letters118040402 American Physical Society

    We explore the joint activated dynamics exhibited by two quantum degrees of freedom: a cavity mode oscillator which is strongly coupled to a superconducting qubit in the strongly coherently driven dispersive regime. Dynamical simulations and complementary measurements show a range of parameters where both the cavity and the qubit exhibit sudden simultaneous switching between two metastable states. This manifests in ensemble averaged amplitudes of both the cavity and qubit exhibiting a partial coherent cancellation. Transmission measurements of driven microwave cavities coupled to transmon qubits show detailed features which agree with the theory in the regime of simultaneous switching

    Joseph L. Allen, Robert Kosut, Jaewoo Joo, Peter Leek, Eran Ginossar (2020)Data for the paper Optimal control of two qubits via a single cavity drive in circuit quantum electrodynamics University of Surrey
    Eran Ginossar, J Joo (2016)Efficient scheme for hybrid teleportation via entangled coherent states in circuit quantum electrodynamics, In: Scientific Reports6 Nature Publishing Group

    We propose a deterministic scheme for teleporting an unknown qubit state through continuous-variable entangled states in superconducting circuits. The qubit is a superconducting two-level system and the bipartite quantum channel is a microwave photonic entangled coherent state between two cavities. A Bell-type measurement performed on the hybrid state of solid and photonic states transfers a discrete-variable unknown electronic state to a continuous-variable photonic cat state in a cavity mode. In order to facilitate the implementation of such complex protocols we propose a design for reducing the self-Kerr nonlinearity in the cavity. The teleporation scheme enables quantum information processing operations with circuit-QED based on entangled coherent states. These include state verification and single-qubit operations with entangled coherent states. These are shown to be experimentally feasible with the state of the art superconducting circuits.

    T Mavrogordatos, P Szafulski, Eran Ginossar, MH Szymanska (2016)Mean-field and quantum-fluctuation dynamics in the driven dispersive Jaynes-Cummings model, In: SPIE Proceedings10142

    In this work we investigate the regime of amplitude bistability in the driven dissipative Jaynes-Cummings (JC) model. We study the semiclassical equation dynamics in contrast to entangled cavity-photon and qubit quantum trajectories, discussing our results in the context of an out-of-equilibrium first order quantum dissipative phase transition for a single JC resonator. Finally, we compare the switching process between metastable states for the two system degrees of freedom by examining a single realization of the random qubit vector in the Bloch sphere next to the intracavity amplitude quasi distributions at given time instants.

    JL Allen, R Kosut, J Joo, P Leek, Eran Ginossar (2017)Optimal control of two qubits via a single cavity drive in circuit quantum electrodynamics, In: Physical Review A: Atomic, Molecular and Optical Physics95(4)042325 American Physical Society

    Optimization of the fidelity of control operations is of critical importance in the pursuit of fault tolerant quantum computation. We apply optimal control techniques to demonstrate that a single drive via the cavity in circuit quantum electrodynamics can implement a high fidelity two-qubit all-microwave gate that directly entangles the qubits via the mutual qubit-cavity couplings. This is performed by driving at one of the qubits’ frequencies which generates a conditional two-qubit gate, but will also generate other spurious interactions. These optimal control techniques are used to find pulse shapes that can perform this two-qubit gate with high fidelity, robust against errors in the system parameters. The simulations were all performed using experimentally relevant parameters and constraints.

    The quasi-degenerate ground state manifold of the anisotropic Ising spin model can encode quantum information, but its degree of protection against local perturbations is known to be only partial. We explain how the coupling between the two ground states can be used to observe signatures of Majorana zero modes in a small controlled chain of qubits. We argue that the protection against certain local perturbations persists across a range of parameters even away from the ideal point. Remarkably, when additional non-local interactions are considered the system enters a phase where the ground states are fully protected against all local field perturbations.

    BR Johnson, MD Reed, AA Houck, DI Schuster, LS Bishop, E Ginossar, JM Gambetta, L DiCarlo, L Frunzio, SM Girvin, RJ Schoelkopf (2010)Quantum non-demolition detection of single microwave photons in a circuit, In: NATURE PHYSICS6(9)pp. 663-667 NATURE PUBLISHING GROUP
    J Joo, M Elliott, DKL Oi, E Ginossar, TP Spiller (2016)Deterministic amplification of Schroedinger cat states in circuit quantum electrodynamics, In: NEW JOURNAL OF PHYSICS18023028 IOP PUBLISHING LTD

    We propose a dynamical scheme for deterministically amplifying photonic Schroedinger cat states based on a set of optimal state-transfers. The scheme can be implemented in strongly coupled qubit-cavity systems and is well suited to the capabilities of state of the art superconducting circuits. The ideal analytical scheme is compared with a full simulation of the open Jaynes-Cummings model with realistic device parameters. This amplification tool can be utilized for practical quantum information processing in non-classical continuous-variable states.

    KW Murch, SJ Weber, KM Beck, E Ginossar, I Siddiqi (2013)Suppression of the radiative decay of atomic coherence in squeezed vacuum, In: Quantum Physics

    Quantum fluctuations of the electromagnetic vacuum are responsible for physical effects such as the Casimir force and the radiative decay of atoms, and set fundamental limits on the sensitivity of measurements. Entanglement between photons can produce correlations that result in a reduction of these fluctuations below the vacuum level allowing measurements that surpass the standard quantum limit in sensitivity. Here we demonstrate that the radiative decay rate of an atom that is coupled to quadrature squeezed electromagnetic vacuum can be reduced below its natural linewidth. We observe a two-fold reduction of the transverse radiative decay rate of a superconducting artificial atom coupled to continuum squeezed vacuum generated by a Josephson parametric amplifier, allowing the transverse coherence time T_2 to exceed the vacuum decay limit of 2T_1. We demonstrate that the measured radiative decay dynamics can be used to tomographically reconstruct the Wigner distribution of the the itinerant squeezed state. Our results are the first confirmation of a canonical prediction of quantum optics and open the door to new studies of the quantum light-matter interaction.

    Th. K. Mavrogordatos, G Tancredi, M Elliott, MJ Peterer, A Patterson, J Rahamim, PJ Leek, E Ginossar, MH Szymanska (2020)Data for the paper "Simultaneous bistability of qubit and resonator in circuit quantum electrodynamics" University of Surrey

    We propose a deterministic scheme for teleporting an unknown qubit through continuous-variable entangled states in superconducting circuits. The qubit is a superconducting two-level system and the bipartite quantum channel is a photonic entangled coherent state between two cavities. A Bell-type measurement performed on the hybrid state of solid and photonic states brings a discrete-variable unknown electronic state to a continuous-variable photonic cat state in a cavity mode. This scheme further enables applications for quantum information processing in the same architecture of circuit-QED such as verification and error-detection schemes for entangled coherent states. Finally, a dynamical method of a self-Kerr tunability in a cavity state has been investigated for minimizing self-Kerr distortion and all essential ingredients are shown to be experimentally feasible with the state of the art superconducting circuits.

    I Neder, E Ginossar (2008)Behavior of electronic interferometers in the nonlinear regime., In: Phys Rev Lett100(19)196806pp. 196806-? American Physical Society

    We investigate theoretically the behavior of the current oscillations in an electronic Mach-Zehnder interferometer (MZI) as a function of its source bias. Recently, the MZI visibility data showed an unexplained lobe pattern with a peculiar phase rigidity. Moreover, the effect did not depend on the MZI path length difference. We argue that these effects may be a new many-body manifestation of particle-wave duality in quantum mechanics. When biasing the interferometer sources so much that multiple electrons are on each arm at any instant in time, quantum shot noise (a particle phenomena) must affect the interference pattern of the electrons that create it. A solution to the interaction Hamiltonian presented here shows that the interference visibility has a lobe pattern with applied bias that has a period proportional to the average path length and independent of the path length difference, together with a phase rigidity.

    Konstantin Yavilberg, Eran Ginossar, Eytan Grosfield (2019)Differentiating Majorana from Andreev bound states in a superconducting circuit, In: Physical Review B100241408 American Physical Society

    We investigate the low-energy theory of a one-dimensional finite capacitance topological Josephson junction. Charge fluctuations across the junction couple to resonant microwave fields and can be used to probe microscopic excitations such as Majorana and Andreev bound states. This marriage between localized microscopic degrees of freedom and macroscopic dynamics of the superconducting phase, leads to unique spectroscopic patterns which allow us to reveal the presence of Majorana fermions among the low-lying excitations.

    Matthew Elliott, Eran Ginossar (2015)Enhancement and state tomography of a squeezed vacuum with circuit quantum electrodynamics, In: Physical Review A: Atomic, Molecular and Optical Physics92013826 American Physical Society

    We study the dynamics of a general quartic interaction Hamiltonian under the influence of dissipation and nonclassical driving. We show that this scenario could be realized with a cascaded superconducting cavity-qubit system in the strong dispersive regime in a setup similar to recent experiments. In the presence of dissipation, we find that an effective Hartree-type decoupling with a Fokker-Planck equation yields a good approximation. We find that the stationary state is approximately a squeezed vacuum, which is enhanced by the Q factor of the cavity but conserved by the interaction. The qubit nonlinearity, therefore, does not significantly influence the highly squeezed intracavity microwave field but, for a range of realistic parameters, enables characterization of itinerant squeezed fields.

    M Elliott, E Ginossar (2016)Applications of the Fokker-Planck equation in circuit quantum electrodynamics, In: Physical Review A: Atomic, Molecular and Optical Physics94(4) http://journals.aps.org/pra/

    We study exact solutions of the steady state behaviour of several non-linear open quantum systems which can be applied to the eld of circuit quantum electrodynamics. Using Fokker-Planck equations in the generalised P-representation we investigate the analytical solutions of two fundamental models. First, we solve for the steady-state response of a linear cavity that is coupled to an approximate transmon qubit and use this solution to study both the weak and strong driving regimes, using analytical expressions for the moments of both cavity and transmon elds, along with the Husimi Q-function for the transmon. Second, we revisit exact solutions of quantum Du ng oscillator which is driven both coherently and parametrically while also experiencing decoherence by the loss of single and pairs of photons. We use this solution to discuss both stabilisation of Schrodinger cat states and the generation of squeezed states in parametric ampli ers, in addition to studying the Q-functions of the di erent phases of the quantum system. The eld of superconducting circuits, with its strong nonlinearities and couplings, has provided access to new parameter regimes in which returning to these exact quantum optics methods can provide valuable insights.

    Matthew Elliott, Jaewoo Joo, Eran Ginossar (2020)Kerr engineering in circuit quantum electrodynamics University of Surrey
    Nguyen H Le, Andrew J Fisher, Neil J Curson, Eran Ginossar (2019)Topological phases of a dimerized Fermi-Hubbard model for semiconductor nano-lattices, In: npj Quantum Information6(1)pp. 1-10

    npj Quantum Information 6, 24 (2020) Motivated by recent advances in fabricating artificial lattices in semiconductors and their promise for quantum simulation of topological materials, we study the one-dimensional dimerized Fermi-Hubbard model. We show how the topological phases at half-filling can be characterized by a reduced Zak phase defined based on the reduced density matrix of each spin subsystem. Signatures of bulk-boundary correspondence are observed in the triplon excitation of the bulk and the edge states of uncoupled spins at the boundaries. At quarter-filling we show that owing to the presence of the Hubbard interaction the system can undergo a transition to the topological ground state of the non-interacting Su-Schrieffer-Heeger model with the application of a moderate-strength external magnetic field. We propose a robust experimental realization with a chain of dopant atoms in silicon or gate-defined quantum dots in GaAs where the transition can be probed by measuring the tunneling current through the many-body state of the chain.

    E Ginossar, Y Levinson, S Levit (2008)Coherent optical control of correlation waves of spins in semiconductors, In: PHYSICAL REVIEW B78(20)ARTN 2pp. ?-? AMER PHYSICAL SOC
    E Ginossar, S Levit (2005)Semiconductor Microstructure in a Squeezed Vacuum: Electron-Hole Plasma Luminescence, In: Physical Review B (Condensed Matter and Materials Physics)72(7)075333 American Physical Society

    We consider a semiconductor quantum-well placed in a wave guide microcavity and interacting with the broadband squeezed vacuum radiation, which fills one mode of the wave guide with a large average occupation. The wave guide modifies the optical density of states so that the quantum well interacts mostly with the squeezed vacuum. The vacuum is squeezed around the externally controlled central frequency $____om_0$, which is tuned above the electron-hole gap $E_g$, and induces fluctuations in the interband polarization of the quantum-well. The power spectrum of scattered light exhibits a peak around $____om_0$, which is moreover non-Lorentzian and is a result of both the squeezing and the particle-hole continuum. The squeezing spectrum is qualitatively different from the atomic case. We discuss the possibility to observe the above phenomena in the presence of additional non-radiative (e-e, phonon) dephasing.

    Eran Ginossar, E Grosfeld (2014)Microwave transitions as a signature of coherent parity mixing effects in the Majorana-transmon qubit, In: NATURE COMMUNICATIONS54772 NATURE PUBLISHING GROUP

    Solid-state Majorana fermions are generating intensive interest because of their unique properties and possible applications in fault tolerant quantum memory devices. Here we propose a method to detect signatures of Majorana fermions in hybrid devices by employing the sensitive apparatus of the superconducting charge-qubit architecture and its efficient coupling to microwave photons. In the charge and transmon regimes of this device, we find robust signatures of the underlying Majorana fermions that are, remarkably, not washed out by the smallness of the Majorana contribution to the Josephson current. It is predicted that at special gate bias points the photon-qubit coupling can be switched off via quantum interference, and in other points it is exponentially dependent on the control parameter EJ/EC. We propose that this device could be used to manipulate the quantum state of the Majorana fermion and realize a tunable high coherence four-level system in the superconducting-circuit architecture.

    E Ginossar, LS Bishop, SM Girvin (2012)Nonlinear oscillators and high fidelity qubit state measurement in circuit quantum electrodynamics, In: Fluctuating Nonlinear Oscillators. From nanomechanics to quantum superconducting circuits(8)pp. 198-? Oxford University Press

    In this book chapter we analyze the high excitation nonlinear response of the Jaynes-Cummings model in quantum optics when the qubit and cavity are strongly coupled. We focus on the parameter ranges appropriate for transmon qubits in the circuit quantum electrodynamics architecture, where the system behaves essentially as a nonlinear quantum oscillator and we analyze the quantum and semi-classical dynamics. One of the central motivations is that under strong excitation tones, the nonlinear response can lead to qubit quantum state discrimination and we present initial results for the cases when the qubit and cavity are on resonance or far off-resonance (dispersive).

    We present a complete classification of the electron-electron interaction in chaotic quantum dots based on expansion in inverse powers of $1/M$, the number of the electron states in the Thouless window, $M ____simeq k_F R$. This classification is quite universal and extends and enlarges the universal non interacting RMT statistical ensembles. We show that existing Coulomb blockade peak spacing data for $B=0$ and $B____ne 0$ is described quite accurately by the interacting GSE and by its extension to $B____ne 0$. The bimodal structure existing in the interacting GUE case is completely washed out by the combined effect of the spin orbit, pairing and higher order residual interactions.

    Themis Marvogordatos (2020)Dark_state_PRA_Themis_2018 University of Surrey
    KW Murch, E Ginossar, SJ Weber, R Vijay, SM Girvin, I Siddiqi (2012)Quantum State Sensitivity of an Autoresonant Superconducting Circuit, In: Physics Review B

    When a frequency chirped excitation is applied to a classical high-Q nonlinear oscillator, its motion becomes dynamically synchronized to the drive and large oscillation amplitude is observed, provided the drive strength exceeds the critical threshold for autoresonance. We demonstrate that when such an oscillator is strongly coupled to a quantized superconducting qubit, both the effective nonlinearity and the threshold become a non-trivial function of the qubit-oscillator detuning. Moreover, the autoresonant threshold is sensitive to the quantum state of the qubit and may be used to realize a high fidelity, latching readout whose speed is not limited by the oscillator Q.

    E Ginossar, Y Levinson, S Levit (2008)Optical manipulation of collective spin correlations in semiconductors with a squeezed vacuum of polarized photons, In: PHYSICAL REVIEW B77(3)ARTN 0pp. ?-? AMER PHYSICAL SOC
    I Rabinak, E Ginossar, S Levit (2007)Atom in a coherently controlled squeezed vacuum, In: PHYSICAL REVIEW A76(1)ARTN 0pp. ?-? AMER PHYSICAL SOC
    LS Bishop, E Ginossar, SM Girvin (2010)Response of the strongly driven Jaynes-Cummings oscillator., In: Phys Rev Lett105(10)100505pp. 100505-? American Physical Society

    We analyze the Jaynes-Cummings model of quantum optics, in the strong-dispersive regime. In the bad-cavity limit and on time scales short compared to the atomic coherence time, the dynamics are those of a nonlinear oscillator. A steady-state nonperturbative semiclassical analysis exhibits a finite region of bistability delimited by a pair of critical points, unlike the usual dispersive bistability from a Kerr nonlinearity. This analysis explains our quantum trajectory simulations that show qualitative agreement with recent experiments from the field of circuit quantum electrodynamics.

    AC Bleszynski-Jayich, WE Shanks, B Peaudecerf, E Ginossar, F von Oppen, L Glazman, JG Harris (2009)Persistent currents in normal metal rings., In: Science326(5950)pp. 272-275 American Association for the Advancement of Science

    Quantum mechanics predicts that the equilibrium state of a resistive metal ring will contain a dissipationless current. This persistent current has been the focus of considerable theoretical and experimental work, but its basic properties remain a topic of controversy. The main experimental challenges in studying persistent currents have been the small signals they produce and their exceptional sensitivity to their environment. We have developed a technique for detecting persistent currents that allows us to measure the persistent current in metal rings over a wide range of temperatures, ring sizes, and magnetic fields. Measurements of both a single ring and arrays of rings agree well with calculations based on a model of non-interacting electrons.

    LS Bishop, L Tornberg, D Price, E Ginossar, A Nunnenkamp, AA Houck, JM Gambetta, J Koch, G Johansson, SM Girvin, RJ Schoelkopf (2009)Proposal for generating and detecting multi-qubit GHZ states in circuit QED, In: NEW JOURNAL OF PHYSICS11ARTN 0pp. ?-? IOP PUBLISHING LTD
    E Ginossar, LS Bishop, DI Schuster, SM Girvin (2010)Protocol for high-fidelity readout in the photon-blockade regime of circuit QED, In: PHYSICAL REVIEW A82(2)ARTN 0pp. ?-? AMER PHYSICAL SOC
    HUY NGUYEN LE, Andrew J. Fisher, ERAN GINOSSAR (2017)Extended Hubbard model for mesoscopic transport in donor arrays in silicon, In: Physical Review B96(24)245406 American Physical Society

    Arrays of dopants in silicon are promising platforms for the quantum simulation of the Fermi-Hubbard model. We show that the simplest model with only on-site interaction is insufficient to describe the physics of an array of phosphorous donors in silicon due to the strong intersite interaction in the system. We also study the resonant tunneling transport in the array at low temperature as a mean of probing the features of the Hubbard physics, such as the Hubbard bands and the Mott gap. Two mechanisms of localization which suppresses transport in the array are investigated: The first arises from the electron-ion core attraction and is significant at low filling; the second is due to the sharp oscillation in the tunnel coupling caused by the intervalley interference of the donor electron's wave function. This disorder in the tunnel coupling leads to a steep exponential decay of conductance with channel length in one-dimensional arrays, but its effect is less prominent in two-dimensional ones. Hence, it is possible to observe resonant tunneling transport in a relatively large array in two dimensions.

    G Matmon, Eran Ginossar, B Villis, A Kolker, T Lim, H Solanki, S Schofield, N Curson, Juerong Li, Benedict Murdin, A Fisher, G Aeppli (2018)2D-3D crossover in a dense electron liquid in silicon, In: Physical Review B97155306 American Physical Society

    Doping of silicon via phosphine exposures alternating with molecular beam epitaxy overgrowth is a path to Si:P substrates for conventional microelectronics and quantum information technologies. The technique also provides a new and well-controlled material for systematic studies of two-dimensional lattices with a half-filled band. We show here that for a dense (ns = 2.8 × 1014 cm−2 ) disordered two-dimensional array of P atoms, the full field angle-dependent magnetostransport is remarkably well described by classic weak localization theory with no corrections due to interaction effects. The two- to three-dimensional cross-over seen upon warming can also be interpreted using scaling concepts, developed for anistropic three-dimensional materials, which work remarkably except when the applied fields are nearly parallel to the conducting planes.

    Jaewoo Joo, Matthew Elliott, Daniel K Oi, Eran Ginossar, Timothy P Spiller (2020)Supporting Data for 'Deterministic amplification of Schrödinger cat states in circuit quantum electrodynamics' University of Surrrey
    Nguyen Le, Andrew J. Fisher, Neil J. Curson, Eran Ginossar (2020)Topological phases of a dimerized Fermi-Hubbard model for semiconductor nano-lattices, In: npj Quantum Information Nature Research (Springer Nature)

    Motivated by recent advances in fabricating artificial lattices in semiconductors and their promise for quantum simulation of topological materials, we study the one-dimensional dimerized Fermi- Hubbard model. We show how the topological phases at half-filling can be characterized by a reduced Zak phase defined based on the reduced density matrix of each spin subsystem. Signatures of bulk-boundary correspondence are observed in the triplon excitation of the bulk and the edge states of uncoupled spins at the boundaries. At quarter-filling we show that owing to the presence of the Hubbard interaction the system can undergo a transition to the topological ground state of the non-interacting Su-Schrieffer-Heeger model with the application of a moderate-strength external magnetic field. We propose a robust experimental realization with a chain of dopant atoms in silicon or gate-defined quantum dots in GaAs where the transition can be probed by measuring the tunneling current through the many-body state of the chain.

    G Kirchmair, B Vlastakis, Z Leghtas, SE Nigg, H Paik, E Ginossar, M Mirrahimi, L Frupzio, SM Girvin, RJ Schoelkopf (2013)Observation of quantum state collapse and revival due to the single-photon Kerr effect, In: NATURE495(7440)pp. 205-209 NATURE PUBLISHING GROUP
    E Ginossar, LI Glazman, T Ojanen, F von Oppen, WE Shanks, AC Bleszynski-Jayich, JGE Harris (2010)Mesoscopic persistent currents in a strong magnetic field, In: PHYSICAL REVIEW B81(15)ARTN 1pp. ?-? AMER PHYSICAL SOC
    K Yavilberg, E Ginossar, E Grosfeld (2014)Fermion parity measurement and control in Majorana circuit quantum electrodynamics, In: PHYSICAL REVIEW B92(7)075143 AMERICAN PHYSICAL SOC

    Combining superconducting qubits with mesoscopic devices that carry topological states of matter may lead to compact and improved qubit devices with properties useful for fault-tolerant quantum computation. Recently, a charge qubit device based on a topological superconductor circuit has been introduced where signatures of Majorana fermions could be detected spectroscopically in the transmon regime. This device stores quantum information in coherent superpositions of fermion parity states originating from the Majorana fermions, generating a highly isolated qubit whose coherence time could be greatly enhanced. We extended the conventional semi-classical method and obtained analytical derivations for strong transmon-photon coupling. The analytical challenge is rendered tractable via a formalism based on the WKB method that allows to extract the energy eigenstates of the qubit and its dipole matrix elements. Using this formalism, we study the effect of the Majorana fermions on the quantum electrodynamics of the device embedded within an optical cavity and develop protocols to initialise, control and measure the parity states. We show that, remarkably, the parity eigenvalue can be detected via dispersive shifts of the optical cavity in the strong coupling regime and its state can be coherently manipulated via a second order sideband transition.

    AC Bleszynski-Jayich, WE Shanks, B Peaudecerf, E Ginossar, FV Oppen, L Glazman, JGE Harris (2009)Persistent currents in normal metal rings: comparing high-precision experiment with theory, In: Science326(5950)pp. 272-275 American Association for the Advancement of Science

    Quantum mechanics predicts that the equilibrium state of a resistive electrical circuit contains a dissipationless current. This persistent current has been the focus of considerable theoretical and experimental work, but its basic properties remain a topic of controversy. The main experimental challenges in studying persistent currents have been the small signals they produce and their exceptional sensitivity to their environment. To address these issues we have developed a new technique for detecting persistent currents which offers greatly improved sensitivity and reduced measurement back action. This allows us to measure the persistent current in metal rings over a wider range of temperature, ring size, and magnetic field than has been possible previously. We find that measurements of both a single ring and arrays of rings agree well with calculations based on a model of non-interacting electrons.