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71
Testing Bell’s Inequality with Ballistic Electrons in Semiconductors
, 2000
"... We propose an experiment to test Bell’s inequality violation in condensedmatter physics. We show how to generate, manipulate and detect entangled states using ballistic electrons in Coulombcoupled semiconductor quantum wires. Due to its simplicity (only five gates are required to prepare entangled ..."
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We propose an experiment to test Bell’s inequality violation in condensedmatter physics. We show how to generate, manipulate and detect entangled states using ballistic electrons in Coulombcoupled semiconductor quantum wires. Due to its simplicity (only five gates are required to prepare entangled states and to test Bell’s inequality), the proposed semiconductorbased scheme can be implemented with currently available technology. Moreover, its basic ingredients may play a role towards largescale quantuminformation processing in solidstate devices.
Distributed Hybrid Quantum Computing
, 2008
"... There are numerous proposals for the physical realization of a quantum computer. However, distributed approaches, making use both of flying and stationary qubits, seem to constitute the most promising route towards a truly scalable device. Such systems guarantee extendibility, they incorporate the i ..."
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There are numerous proposals for the physical realization of a quantum computer. However, distributed approaches, making use both of flying and stationary qubits, seem to constitute the most promising route towards a truly scalable device. Such systems guarantee extendibility, they incorporate the interface with communication applications and relax the physical realization of the device, allowing for defect tolerance. Flying qubits are included in the more general concept of a quantum bus, a mediating system which can be of higher dimension. Such a quantum bus can be used in the straightforward preparation of a standard multiqubit resource enabling measurement based quantum computation, the cluster state. This constitutes the framework for the results presented in this thesis. We begin by investigating the effects of dissipation in the continuous variable bus scheme known as the qubus scheme. By considering loss in the bus as it mediates interactions between the stationary qubits, we obtain analytical results for the effective action of the induced quantum gate. We find
1 HighLevel Interconnect Model for the Quantum Logic Array Architecture
, 2008
"... We summarize the main characteristics of the quantum logic array (QLA) architecture with a careful look at the key issues not described in the original conference publications: primarily, the teleportationbased logical interconnect. The design goal of the the quantum logic array architecture is to ..."
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We summarize the main characteristics of the quantum logic array (QLA) architecture with a careful look at the key issues not described in the original conference publications: primarily, the teleportationbased logical interconnect. The design goal of the the quantum logic array architecture is to illustrate a model for a largescale quantum architecture that solves the primary challenges of systemlevel reliability and data distribution over large distances. The QLA’s logical interconnect design, which employs the quantum repeater protocol, is in principle capable of supporting the communication requirements for applications as large as the factoring of a 2048bit number using Shor’s quantum factoring algorithm. Our physicallevel assumptions and architectural component validations are based on the trapped ion technology for implementing quantum computing.
Spin Electronics and Spin Computation
, 2001
"... We review several proposed spintronic devices that can provide new functionality or improve available functions of electronic devices. In particular, we discuss a high mobility field effect spin transistor, an allmetal spin transistor, and our recent proposal of an allsemiconductor spin transistor ..."
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We review several proposed spintronic devices that can provide new functionality or improve available functions of electronic devices. In particular, we discuss a high mobility field effect spin transistor, an allmetal spin transistor, and our recent proposal of an allsemiconductor spin transistor and a spin battery. We also address some key issues in spinpolarized transport, which are relevant to the feasibility and operation of hybrid semiconductor devices. Finally, we discuss a more radical aspect of spintronic research—the spinbased quantum computation and quantum information processing. I.
Verified Delegated Quantum Computing with One Pure Qubit
, 2014
"... While building a universal quantum computer remains challenging, devices of restricted power such as the socalled one pure qubit model have attracted considerable attention. An important step in the construction of these limited quantum computational devices is the understanding of whether the ver ..."
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While building a universal quantum computer remains challenging, devices of restricted power such as the socalled one pure qubit model have attracted considerable attention. An important step in the construction of these limited quantum computational devices is the understanding of whether the verification of the computation within these models could be also performed in the restricted scheme. Encoding via blindness (a cryptographic protocol for delegated computing) has proven successful for the verification of universal quantum computation with a restricted verifier. In this paper, we present the adaptation of this approach to the one pure qubit model, and present the first feasible scheme for the verification of delegated one pure qubit model of quantum computing. 1
QUANTUM SIMULATION IN STRONGLY CORRELATED OPTICAL LATTICES
, 2012
"... An outstanding problem in physics is how to understand strongly interacting quantum manybody systems such as the quarkgluon plasma, neutron stars, superfluid 4He, and the hightemperature superconducting cuprates. The physics approach to this problem is to reduce these complex systems to minimal m ..."
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An outstanding problem in physics is how to understand strongly interacting quantum manybody systems such as the quarkgluon plasma, neutron stars, superfluid 4He, and the hightemperature superconducting cuprates. The physics approach to this problem is to reduce these complex systems to minimal models that are believed to retain relevant phenomenology. For example, the Hubbard model — the focus of this thesis — describes quantum particles tunneling between sites of a lattice with onsite interactions. The Hubbard model is conjectured to describe the lowenergy charge and spin properties of hightemperature superconducting cuprates. Thus far, there are no analytic solutions to the Hubbard model, and numerical calculations are difficult and even impossible in some regimes (e.g., the FermiHubbard model away from halffilling). Therefore, whether the Hubbard model is a minimal model for the cuprates remains unresolved. In the face of these difficulties, a new approach has emerged — quantum simulation. The premise of quantum simulation is to perform experiments on a quantum system that is welldescribed by the model we are trying to study, has tunable parameters, and is easily probed. Ultracold atoms trapped in optical lattices are an ideal candidate for quantum simulation of the Hubbard models. This thesis describes work on two such systems: a 87Rb (boson) optical lattice experiment in the group of Brian DeMarco at the University
Quantum Information Processing and Quantum Control with Trapped Atomic Ions
 Phys. Scr. 2009
"... The role of trapped atomic ions in the field of quantum information processing is briefly reviewed. We discuss some of the historical developments that enabled ions to enter the field and then summarize the basic mechanisms required for logic gates and the use of the gates in demonstrating simple al ..."
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The role of trapped atomic ions in the field of quantum information processing is briefly reviewed. We discuss some of the historical developments that enabled ions to enter the field and then summarize the basic mechanisms required for logic gates and the use of the gates in demonstrating simple algorithms. We describe potential pathways to reach faulttolerant error levels and largescale devices, and highlight some of the main problems that will be faced in achieving these goals. Possible nearterm applications in applied and basic science, such as in metrology and quantum simulation, are discussed. PACS numbers: 03.67.−a, 03.67.Ac, 37.10.Ty (Some figures in this article are in colour only in the electronic version.) 1.
Ultrafast Control of Spin and Motion in Trapped Ions
, 2013
"... Trapped atomic ions are a promising medium for quantum computing, due to their long coherence times and potential for scalability. Current methods of entangling ions rely on addressing individual modes of motion within the trap and applying qubit state dependent forces with external fields. This ap ..."
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Trapped atomic ions are a promising medium for quantum computing, due to their long coherence times and potential for scalability. Current methods of entangling ions rely on addressing individual modes of motion within the trap and applying qubit state dependent forces with external fields. This approach can limit the speed of entangling gates and make them vulnerable to decoherence due to coupling to unwanted modes or ion heating. This thesis is directed towards demonstrating novel entanglement schemes which are not limited by the trap frequency, and can be made almost arbitrarily fast. Towards this goal, I report here on the first experiments using ultrafast laser pulses to control the internal and external states of a single trapped ion. I begin with experiments in ultrafast spin control, showing how a single laser pulse can be used to completely control both spin degrees of freedom of the ion qubit in tens of picoseconds. I also show how a train of weak pulses can be used to drive Raman transitions based on a frequency comb. I then discuss experiments using pulses to rapidly entangle the spin with the motion, and how careful spectral redistribution allows a single pulse to execute a spindependent momentum kick. Finally, I explain how these spindependent momentum kicks can be used in the future to create an ultrafast entangling gate. I go over how such a gate would work, and present experimentally realizable timing sequences which would create a maximally entangled state of two ions in a time faster than the period of motion in the trap.