Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 68, Number 7
Monday–Friday, June 5–9, 2023; Spokane, Washington
Session Q10: Advances in Quantum Gates |
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Chair: Nathan Lysne, National Institute of Standards and Technology Room: 207 |
Thursday, June 8, 2023 8:00AM - 8:12AM |
Q10.00001: Raman Gates in Trapped 133Ba+ Zachary J Wall, Samuel Vizvary We present advances in the operation of the synthetic 133Ba+ trapped ion qubit, which was recently used to demonstrate record-breaking qubit state preparation and measurement (SPAM) fidelity. We will present new capabilities for manipulations of the 2S1/2 ground state qubit using raman gates with a far detuned laser. We will also show operations in the metastable 2D5/2 hyperfine states, as well as our progress towards single and two qubit gates within the 2D5/2 hyperfine states. |
Thursday, June 8, 2023 8:12AM - 8:24AM |
Q10.00002: Floquet-engineered holonomic gates in an atomic spin system Logan W Cooke, Arina Tashchilina, Mason Protter, Joseph Lindon, Tian Ooi, Frank Marsiglio, Joseph Maciejko, Lindsay J LeBlanc Holonomic gates consist of loops in some control-parameter space that produce non-Abelian geometric phases, which may couple states within a degenerate manifold. As an approach to universal quantum computing, there have been many successful demonstrations, yet large scale implementations remain elusive in part because of the required robust degeneracies. Recently, several proposals have shown that Floquet engineering may be used to surpass this issue. We demonstrate this concept in a BEC of Floquet-engineered rubidium-87 atoms, where fast periodic driving results in the required degeneracies between atomic spin states and their subsequent holonomic evolution. We characterize these gates by their fidelities and by measurement of the gauge-invariant Wilson-loop, and discuss the various pros and cons of the control scheme as applied to universal quantum computing. |
Thursday, June 8, 2023 8:24AM - 8:36AM |
Q10.00003: Raman scattering errors in hyperfine trapped-ion qubits and implementation of Raman gates in the metastable state Gabriel J Gregory, Alexander D Quinn, Isam D Moore, Jeremy M Metzner, Sean J Brudney, Wes Campbell, Eric R Hudson, Mathew J Buguslawski, David J Wineland, David T Allcock Characterization of single and two qubit gates in metastable states (m qubits) is essential for realizing the omg scheme, which would allow for multi-species functionality with a single ion species [1]. We present an implementation of m qubits in the D5/2 manifold of 40Ca+. Single-qubit Raman gates in m qubits are demonstrated and characterized. We use 976 nm Raman beams (tuned 44 THz red of the 854 nm P3/2 <-> D5/2 transition) in order to achieve low spontaneous Raman scattering errors. We compare these observed scattering errors to theory, accounting for effects relevant at large detunings and we present experimental progress towards implementing a two qubit Mølmer-Sørensen gate using the far-detuned Raman beams. We also consider these effects in models for Raman scattering in qubits in the S1/2 manifold (g qubits) and predict markedly different scattering behavior [2] in the far-detuned regime than previous models. |
Thursday, June 8, 2023 8:36AM - 8:48AM |
Q10.00004: Implementing Robust Nondemolition Readout on Molecular Qubits via Electric-Field Gradient Gates Clayton Z Ho, Grant D Mitts, Hao Wu, Eric R Hudson Due to their rich, radio-frequency addressable rovibrational structure, molecular ions have been proposed as a promising candidate on which to realize a scalable and high-fidelity trapped ion quantum computer (Phys. Rev. Lett. 2020, 125, 120501). One such architecture is Electric-Gradient Gates (EGGs) (Phys. Rev. A. 2021, 104, 042605), which encodes qubits on a molecular ion and uses a co-trapped atomic ion for sympathetic cooling and ancilla readout. With EGGS, a complete and laser-free set of quantum logic operations is achieved through the application of radio-frequency voltages on trap electrodes. Notably, a quantum nondemolition state detection scheme can be implemented by applying bichromatic microwave electric fields at the secular frequency sidebands of a molecular transition to sympathetically heat a co-trapped atomic ion. |
Thursday, June 8, 2023 8:48AM - 9:00AM |
Q10.00005: Individual addressing of trapped ion qubits with geometric phase gates Robert T Sutherland, Raghavendra Srinivas, David T Allcock We propose a new scheme for individual addressing of trapped ion qubits, selecting them via their motional frequency. We show that geometric phase gates can perform single-qubit rotations using the coherent interference of spin-independent and (global) spin-dependent forces. The spin-independent forces, which can be generated via localised electric fields, increase the gate speed while reducing its sensitivity to motional decoherence, which we show analytically and numerically. While the scheme applies to most trapped ion experimental setups, we numerically simulate a specific laser-free implementation, showing cross-talk errors below 1e-6 for reasonable parameters. |
Thursday, June 8, 2023 9:00AM - 9:12AM |
Q10.00006: Towards entangling gates between bosonic qubits in trapped ions Martin Wagener, Stephan Welte, Moritz Fontboté Schmidt, Ivan Rojkov, Edgar Brucke, Hendrik Timme, Ralf Berner, Matteo Marinelli, Ilia Sergachev, Florentin Reiter, Daniel Kienzler, Jonathan Home Encoding quantum information in a harmonic oscillator offers a resource efficient method for quantum error correction, compared to the use of multiple two-level systems. The Gottesman-Kitaev-Preskill (GKP) encoding [1] is particularly promising and has recently been realized in both trapped ions [2, 3] and superconducting microwave cavities [4]. |
Thursday, June 8, 2023 9:12AM - 9:24AM |
Q10.00007: Benchmarking multi-qubit gates in neutral atom systems Bharath Hebbe Madhusudhana Multi-qubit gates are unitary operators generated by many-body Hamiltonians which act non-trivially on >2 (if not all) qubits. They can be naturally implemented in, for example, Rydberg atoms trapped in a tweezer array. They expand the control toolbox of quantum devices, making it over-complete and thus bolstering the optimization of experimental errors when designing a circuit. Moreover, they also carry the potential to achieve practical quantum advantage faster than with circuits using 1 and 2-qubit gates [1]. However, benchmarking such gates is challenging for two reasons: multi-qubit gates are represented by exponentially large unitary matrices, and therefore the corresponding process tomography is not scalable and this unitary cannot always be calculated theoretically, sometimes desirably so, leaving no reference to benchmark experimental data against. Therefore, developing new approaches to benchmarking multi-qubit gates is highly desirable. |
Thursday, June 8, 2023 9:24AM - 9:36AM |
Q10.00008: A quantum perceptron gate and a classical Toffoli gate with microwave-driven trapped ions Patrick Huber, Patrick Barthel, Sougato Bose, Juan José García-Ripoll, Johann Haber, Yasser Omar, Sagar Pratapsi, Erik Torrontegui, Christof Wunderlich Direct implementation of multi-qubit gates with three or more qubits circumvents decomposition into two-qubit operations, effectively reducing the required depth of quantum circuits. Using the inherent all-to-all coupling in a trapped ion quantum computer, we experimentally realize classical Toffoli and quantum perceptron gates with three microwave-driven hyperfine qubits using 171Yb+ ions. The classical Toffoli gate can be used to efficiently implement arithmetic operations, such as a half-adder. The perceptron gate, when nested with other perceptrons, can be used as universal approximator. Both, the perceptron and Toffoli gates are implemented by a continuous microwave driving field, while the qubits’ coherence is protected by pulsed dynamical decoupling. In case of the perceptron, a dressing field applied to the target qubit is adiabatically ramped down. We report the implementation of a two-layer neural network using successive perceptron gates. For the Toffoli gate, the target qubit is controlled by two control qubits and a top hat microwave pulse. 171Yb+ ions are stored in a linear Paul trap exposed to a permanent magnetic field gradient. Using MAgnetic Gradient Induced Coupling (MAGIC), all-to-all coupling in the qubit register is achieved while the qubits can be individually addressed by microwave radiation. |
Thursday, June 8, 2023 9:36AM - 9:48AM |
Q10.00009: Efficient multi-qubit gates for simulating chemical dynamics in trapped-ion quantum computers Alexander Rasmusson, Thomas Burkle, Philip Richerme Simulating the dynamics of quantum chemical systems is a promising application of quantum computers. While most quantum algorithms and experimental demonstrations have focused on calculations of electronic structure in molecules, a recently developed protocol [1] proposed techniques to simulate nuclear dynamics in a Hydrogen-bonded system and was recently demonstrated in a trapped-ion quantum computer [2]. Here we propose a more efficient decomposition of Hamiltonians which describe proton transfer in chemical systems using multi-qubit gates and single qubit rotations. Leveraging the all-to-all connectivity of global Molmer-Sorensen interactions in trapped-ion systems, we show an efficient decomposition into layers of global multi-qubit gates and local single qubit rotations. We present a thorough study of the experimental feasibility of our approach and comparison against more common universal gate sets available in generic quantum computers. Our proposal offers the potential to perform efficient simulation of quantum chemical dynamics on trapped-ion quantum simulators well into the regime of classical intractability. |
Thursday, June 8, 2023 9:48AM - 10:00AM |
Q10.00010: Non-Local Multi-Qubit Quantum Gates via a Driven Bosonic Mode Vineesha Srivastava, Sven Jandura, Gavin K Brennen, Guido Pupillo Native Non-Local quantum gates are essential for efficient implementation of quantum circuits in the Noisy-Intermediate-Scale-Quantum(NISQ) era quantum devices, and for Quantum Error Correction in the future. In this regard, we present two protocols for implementing deterministic non-local multi-qubit quantum gates on qubits coupled to a common bosonic mode e.g. a cavity field. In contrast to previous proposals, our protocols only rely on a classical drive of the bosonic mode, while no external drive of the qubits is required. In the first protocol, the state of the bosonic mode follows a closed trajectory in phase space and accumulates a geometric phase depending on the state of the qubits. The second protocol instead uses an adiabatic evolution of the combined qubit and bosonic mode system to accumulate a dynamical phase. For both protocols, we provide analytic solutions for the error rates in the presence of losses. Our protocols are applicable to a variety of systems, including cold atoms and molecules in cavities, trapped ions coupled via a motional mode, and superconducting qubits coupled to a microwave resonator. |
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