Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session J37: Focus Session: Quantum Dynamics with Phonons and Photons |
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Sponsoring Units: GQI Chair: Ken Brown, Georgia Institute of Technology Room: 212A |
Tuesday, March 3, 2015 2:30PM - 3:06PM |
J37.00001: Quantum Information Experiments with Trapped Ions at NIST Invited Speaker: Andrew Wilson We present an overview of recent trapped-ion quantum information experiments at NIST. Advancing beyond few-qubit ``proof-of-principle'' experiments to the many-qubit systems needed for practical quantum simulation and information processing, without compromising on the performance demonstrated with small systems, remains a major challenge. One approach to scalable hardware development is surface-electrode traps. Micro-fabricated planar traps can have a number of useful features, including flexible electrode geometries, integrated microwave delivery, and spatio-temporal tuning of potentials for ion transport and spin-spin interactions. In this talk we report on a number of on-going investigations with surface traps. Experiments feature a multi-zone trap with closely spaced ions in a triangular arrangement (a first step towards 2D arrays of ions with tunable spin-spin interactions), a scheme for smooth transport through a junction in a 2D structure based on switchable RF potentials, and a micro-fabricated photo-detector integrated into a trap. We also give a progress report on our latest efforts to improve the fidelity of both optical and microwave 2-qubit gates. This work was supported by IARPA, ONR and the NIST Quantum Information Program. The 3-ion and switchable-RF-junction traps were developed in collaboration with Sandia National Laboratory. [Preview Abstract] |
Tuesday, March 3, 2015 3:06PM - 3:18PM |
J37.00002: Trapped Ion Quantum Computing with Microwaves Joe Randall, Sebastian Weidt, Eamon Standing, Simon Webster, Kim Lake, David Murgia, Tomas Navickas, Bjoern Lekitsch, Marcus Hughes, Robin Sterling, Darren De Motte, Gouri Giri, Andrea Rodriguez, Anna Webb, Hwanjit Rattanasonti, Prasanna Srinivasan, Michael Kraft, Jessica Maclean, Chris Mellor, Winfried Hensinger To this point, entanglement operations in trapped ion~qubits~have been predominantly~performed with lasers. However, this becomes problematic when scaling to large numbers of~qubits~due to the challenging engineering~required. The use of stable and easily controllable microwaves to drive entanglement gates can overcome this problem.~ We will present our work towards implementing multi-qubit~entanglement gates using microwaves in an experimental setup that produces a~static~magnetic field gradient of 24 T/m over an ion string. We will first present a scheme for preparing and manipulating~dressed-state~qubits~and~qutrits~that are highly~robust~to~decoherence~from~magnetic field fluctuations. We will~also~present our~work~experimentally~demonstrating motional sideband transitions and~Schr\"{o}dinger cat states using~microwaves in conjunction with~the~magnetic field~gradient, as well as~sideband cooling to the ground state of motion using~dressed-states. Furthermore, we will show our latest results in creating~microfabricated~ion trap chips~towards large scale~quantum computing and~simulation.~~ [Preview Abstract] |
Tuesday, March 3, 2015 3:18PM - 3:30PM |
J37.00003: Non-Hermitian magnetism and entanglement in dissipative atomic systems Tony Lee, Ching-Kit Chan, Florentin Reiter, Nimrod Moiseyev Quantum phase transitions are usually studied in terms of Hermitian Hamiltonians. However, cold-atom experiments can implement non-Hermitian Hamiltonians via weak measurements. We show that the non-Hermitian XY model exhibits quantum phase transitions beyond the framework of Hermitian physics. There is a phase transition already for two atoms. In a 1D chain, the ordered phase is frustrated and has quasi-long-range order despite the absence of a continuous symmetry [1]. The non-Hermitian phase transition also has a lot more entanglement than the Hermitian one [2]. We discuss experimental implementation with trapped ions, cavity QED, and optical lattices. [1] Phys. Rev. X 4, 041001 (2014). [2] arXiv:1409.7067. [Preview Abstract] |
Tuesday, March 3, 2015 3:30PM - 3:42PM |
J37.00004: Entanglement Transfer in a Double Jaynes-Cummings Model Samina Masood, Allen Miller We compute and analyze the atom-atom entanglement, the entanglement between the two photon modes, and also the entanglement between each atom and each photon mode. The measure of entanglement is the von Neumann entropy. For the case in which the two atom-photon systems have identical properties, but allowing for non-resonant conditions, the sum of the atom-atom and photon-modes-entanglement is time-independent. [Preview Abstract] |
Tuesday, March 3, 2015 3:42PM - 4:18PM |
J37.00005: Quantum dynamics of interacting spins mediated by phonons and photons Invited Speaker: Crystal Senko Techniques that enable robust, controllable interactions among quantum particles are now being actively explored. They constitute a key ingredient for quantum information processing and quantum simulations. We describe two atom-based platforms to experimentally realize and study quantum dynamics with controllable, long-range spin-spin interactions. Using trapped atomic ions, we implemented tunable spin-spin interactions mediated by optical dipole forces, which represent a new approach to study quantum magnetism. This platform has enabled sophisticated manipulations of more than 10 spins, and realization of quantum simulations of integer-spin chains. In a separate set of experiments we realized a hybrid system in which single photons, confined to sub-wavelength dimensions with a photonic crystal cavity, are coupled to single trapped neutral atoms. Extending this architecture to multiple atoms enables photon-induced quantum gates, and tunable spin-spin interactions, between distant atoms. [Preview Abstract] |
Tuesday, March 3, 2015 4:18PM - 4:30PM |
J37.00006: ABSTRACT WITHDRAWN |
Tuesday, March 3, 2015 4:30PM - 4:42PM |
J37.00007: On Readout of Vibrational Qubits using Quantum Beats Dmytro Shyshlov, Dmitri Babikov Readout of the final states of qubits is a crucial step towards implementing quantum computation in experiment. In this theoretical work we explore the process of readout from vibrational qubits in thiophosgene molecule, SCCl2, using quantum beat oscillations. The quantum beats are measured by first exciting the superposition of the qubit-encoding vibrational states to the electronically excited readout state with variable time delay pulses. The resulting oscillation of population of the readout state is then detected as a function of time delay. In principle, fitting the quantum beat signal by an analytical expression should allow extracting the values of probability amplitudes and the relative phases of the vibrational qubit states. However, we found that if this procedure is implemented using the standard analytic expression for quantum beats, a non-negligible phase error is obtained. We discuss the origin and properties of this phase error, and propose a new analytical expression to correct the phase error. The corrected expression fits the quantum beat signal very accurately. We now have a practical approach to read out the final state of vibrational qubits in experiments by combining the analytic expression for fitting with numerical modelling of the readout process. [Preview Abstract] |
Tuesday, March 3, 2015 4:42PM - 4:54PM |
J37.00008: ABSTRACT WITHDRAWN |
Tuesday, March 3, 2015 4:54PM - 5:06PM |
J37.00009: Proof of Monogamy of non-local correlations in three and four qubit states Santosh Shelly Sharma, Naresh Kumar Sharma Recently, we used the process of selective construction of invariants to obtain physically meaningful polynomial invariants for three and four qubit pure states. In this article, we report the exact relations between the concurrence of a two qubit reduced state and corresponding three or four qubit pure state invariants. Firstly, we obtain an analytical expression for concurrence of a given mixed state of two qubits in terms of determinants of negativity fonts in the three or four qubit pure state. For three qubits, a comparison with three tangle and squared negativity expressed in terms of determinants of negativity fonts leads to three relations. These three conditions satisfied by the two-way and three-way correlations sum together and lead to well known CKW inequality. When a qubit pair is part of a four qubit pure state, it may be entangled to the rest of the system through two-way, three-way and four-way correlations. Monogamy equalities, satisfied by two-way, three-way and four-way non-local quantum correlatios are presented for states belonging to classes of four qubit pure states with distinct entanglement types. [Preview Abstract] |
Tuesday, March 3, 2015 5:06PM - 5:18PM |
J37.00010: Quantum error prevention and leakage elimination for quantum dots Saeed Pegahan, Mark S. Byrd, Karthik Reddy Chinni Decoherence-free, or noiseless subsystems, are used to encode spin qubits in quantum dots in order to achieve universal quantum computing using only the exchange interaction. We investigate the use of dynamical decoupling controls for the purposes of eliminating leakage for a logical qubit encoded using three physical qubits. These leakage elimination operators (LEOs) can be used to eliminate all leakage errors using exchange interactions between the physical spin qubits. Depending on the encoding and the decoupling control, different types of errors can be eliminated. We show several different possible controls and the consequential noise reduction for different encodings as well as our general method for determining the effectiveness of these pulses. [Preview Abstract] |
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