Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 67, Number 7
Monday–Friday, May 30–June 3 2022; Orlando, Florida
Session C06: New Frontiers for Quantum Computing with Neutral AtomsRecordings Available
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Chair: Adam Kaufman, JILA,CU Boulder Room: Salon 1/2 |
Tuesday, May 31, 2022 11:00AM - 11:12AM |
C06.00001: Any-to-any connected cavity-mediated architecture for quantum computing with trapped ions or Rydberg arrays Joshua Ramette, Josiah J Sinclair, Zachary Vendeiro, Alyssa Rudelis, Marko Cetina, Vladan Vuletic We present a newly proposed hardware architecture and protocol for connecting many local quantum processors contained within an optical cavity. The scheme is compatible with trapped ions or Rydberg arrays and realizes teleported gates between any two qubits by distributing entanglement via single-photon transfers through a cavity. In contrast to previous proposals for quantum computing with optical cavities, we employ heralding to achieve high-fidelity entanglement even with a cavity of moderate quality. For processors composed of trapped ions in a linear chain, a single cavity with realistic parameters successfully transfers photons every few μs, enabling the any-to-any entanglement of 20 ion chains containing a total of 500 qubits in 200 μs with both fidelities and rates limited only by local operations and ion readout. For processors composed of Rydberg atoms, our method fully connects a large array of thousands of neutral atoms. The connectivity afforded by our architecture is extendable to tens of thousands of qubits using multiple overlapping cavities, expanding capabilities for NISQ era algorithms and Hamiltonian simulations, as well as enabling more robust high-dimensional error-correcting schemes. |
Tuesday, May 31, 2022 11:12AM - 11:24AM |
C06.00002: Reducing the Sensitivity of Quantum Gates to Laser Intensity Noise via Real-Time Feedback on Gate Parameters Ramon Szmuk, Yoav Romach, Niv Drucker Quantum processors using laser fields to drive qubits suffer from laser intensity fluctuations which limit gate fidelities [1-4]. Mitigation of such noise processes via feedback was up until now only available via low bandwidth sequencers running on CPUs (allowing at best for shot to shot corrections) or on FPGA processors and analog circuits that take orders of magnitude longer to develop and iterate on. |
Tuesday, May 31, 2022 11:24AM - 11:36AM |
C06.00003: Two-qubit Quantum Logic Gates for Neutral Atoms Based on the Spin-Flip Blockade Sri Datta Vikas V Buchemmavari, Ivan H Deutsch, sivaprasad T Omanakuttan, Yuan-Yu Jau In the seminal experiment, Jau et al. [1] demonstrated the "spin-flip blockade". Analogous to the "Rydberg blockade", here the spin of one neutral alkali atom in its ground state is allowed to flip between hyperfine manifolds while the two-spins are blockaded from flipping simultaneously due to the additional energy imparted by the light-shift in the presence of Rydberg dressing, due to the dipole-dipole interaction of Rydberg states. This spin-flip blockade was used to demonstrate the generation of Bell states with fidelity >81%. We describe here how to extend this to generate universal two-qubit quantum logic gates. We show that many protocols designed for the optical regime can be translated into the microwave regime and analyze their potential for high-fidelity operation. In comparison to the optical protocols, the microwave Raman lasers afford us ultra-precise control which results in the potential for fast quantum logic gates with reduced noise and low decoherence. |
Tuesday, May 31, 2022 11:36AM - 11:48AM |
C06.00004: Experimental roadmap for performing optimal state transfer and entanglement generation in power-law interacting systems Andrew Guo, Jeremy T Young, Ron Belyansky, Przemek Bienias, Alexey V Gorshkov Experimental systems with power-law interactions have attracted interest as promising platforms for quantum information processing. Such systems are capable of spreading entanglement superballistically and achieving an asymptotic speed-up over locally interacting systems, as shown in Eldredge et al. (PRL '17) and Tran et al. (PRX '19). In this work, we provide an experimental roadmap towards realizing two protocols for transferring quantum states in subpolynomial time in three classes of atomic and molecular systems with dipolar interactions: polar molecules composed of alkali-metal dimers, neutral atoms in excited Rydberg states, and atoms with strong magnetic moments. We also numerically evaluate the tradeoffs between the two protocols for small system sizes as a guide to near-term experimental implementation. |
Tuesday, May 31, 2022 11:48AM - 12:00PM |
C06.00005: Robust and High-Fidelity Molecular Qubit Operations via Electric-Field Gradient Gates Clayton Z Ho, Grant D Mitts, Hao Wu, Eric R Hudson Despite the high fidelities achievable with trapped atomic ion qubits, their suitability as a platform for quantum computation is impaired by their use of lasers to effect quantum operations, which both require near-ground-state cooling to reach the Lamb-Dicke regime and introduce errors via spontaneous emission. However, it was recently shown (PhysRevA. 2021, 104, 042605) that radio-frequency voltages applied to trap electrodes could be used to achieve a complete, laser-free set of quantum logic operations of molecular ions - Electric Gradient Gates (EGGs). We will discuss EGGs and present numerical simulations that show high-fidelity single- and two-qubit gates are possible in a realistic environment. |
Tuesday, May 31, 2022 12:00PM - 12:12PM |
C06.00006: Counter-factual carving exponentially improves many-body carved state fidelity Joshua Ramette, Josiah J Sinclair, Vladan Vuletic We propose a new, "counter-factual" method for carving a broad class of entangled states of many atoms coupled to a cavity mode, resulting in an exponentially better scaling of the carved state infidelity with the cavity cooperativity compared to previous methods. For many atoms initialized in a classical spin coherent state, different non-classical spin components, or Dicke states, shift the Lorentzian cavity lineshape by an amount dependent on the atom-cavity coupling strength. For a finite energy shift between different Dicke states, the polynomial tail of the lineshape means that directly probing the shifted spectrum can only herald a nonclassical state with an infidelity scaling polynomially with the cavity quality. Instead, we propose addressing a single photon "source atom" within the cavity with a spectrum of tones tuned to the shifted cavity resonances to engineer photon emission rates which depend on the atomic ensemble state. A heralding measurement of the internal state of the source atom consistent with no photon emission projects the ensemble onto a state where the faster decaying spin components have been exponentially suppressed. Carving "counter-factually," by post-selecting on events where a photon was never emitted from the source atom, then enables an exponentially better scaling of the carved state fidelity with the cavity cooperativity. Applying many tones to the source atom allows arbitrary amplitude and phase control of the Dicke state components. Applications of the method include producing high-fidelity many-atom Dicke states and GHZ states useful for quantum metrology, and graph states useful for measurement based quantum computing. |
Tuesday, May 31, 2022 12:12PM - 12:24PM |
C06.00007: Holonomic Quantum Computing in Ultracold Neutral Atoms via Floquet Engineering Logan W Cooke, Arina Tashchilina, Joseph Lindon, Tian Ooi, Taras Hrushevskyi, Lindsay J LeBlanc Holonomic quantum computing (QC) aims to be an intrinsically fault-tolerant alternative to conventional QC techniques; it utilizes non-Abelian geometric phases in highly degenerate systems to realize universal unitary transformations of states in the manifold. While there have been many successful implementations, a scalable platform remains elusive in large part because of the required degeneracy; 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. In particular, we utilize Wilson loops to show that the geometric phase is non-Abelian in a fully gauge-invariant manner; this is required for the protocol to be truly holonomic. Our results for spin-1 transformations are shown along with numerical simulations, and we discuss the protocol's efficacy as a real-world QC model. |
Tuesday, May 31, 2022 12:24PM - 12:36PM |
C06.00008: Quantum Signal Processing and Optimal Hamiltonian Simulation using Rydberg Atoms Sina Zeytinoglu, Sho Sugiura Quantum algorithms promise an immense improvement to our current information processing capabilities by utilizing interference phenomena in an large Hilbert space. However, the large size of the Hilbert space also poses a crucial challenge to the experimentalists, who strive to design protocols that navigate the Hilbert space using only a small number of semiclassical control fields. Here, we design a set of multi-qubit Rydberg blockade gates that provide a solution to this control challenge. These gates are inspired by the recent developments in Quantum Signal Processing (QSP), a framework that unifies a vast number of quantum algorithms. We show that the proposed blockade gates facilitate a (i) robust (ii) shallow depth and (iii) scalable implementation of the so-called block-encoding unitary, the building block of the QSP framework. To showcase our approach, we construct explicit blueprints to implement QSP-based near-optimal Hamiltonian simulation on the Rydberg atom platform. Our protocols improve the gate overhead for implementing the product formula-based near-optimal simulation algorithm by more than an order of magnitude. |
Tuesday, May 31, 2022 12:36PM - 12:48PM |
C06.00009: Demonstrating device benchmarking for useful quantum applications Adam L Shaw, Joonhee Choi, Ran Finkelstein, Pascal Scholl, Daniel Mark, Soonwon Choi, Manuel Endres Using a Rydberg atom-array quantum simulator, we experimentally demonstrate new applications which become possible through verifiable quantum evolution, and further develop our recently proposed protocol for estimating the fidelity of producing non-trivial states for this purpose. At the outset, we show experimental benchmarking with as many as 33 qubits with a small (~5000) number of measurements and show potential scaling to as many as 100 qubits. This protocol is then adapted for the application of target state benchmarking, where we prepare interesting quantum states, and quantitatively measure their preparation fidelity. Along similar lines, we demonstrate in situ learning of local Hamiltonian parameters, and progress towards closed-loop optimization of state preparation control. These new developments showcase practically useful applications for device benchmarking protocols in quantum devices, and further demonstrate a path towards quantum advantage with a near term quantum simulator. |
Tuesday, May 31, 2022 12:48PM - 1:00PM |
C06.00010: Fast Preparation and Detection of a Rydberg Qubit Using Atomic Ensembles Wenchao Xu, Aditya V Venkatramani, Sergio H Cantu, Tamara Sumarac, Valentin Klusener, Emily Qiu, Matthew Peters, Mikhail Lukin, Vladan Vuletic Arrays of neutral atoms have recently emerged as a competitive platform for quantum simulation and computation with many properties favorable for scaling. Rydberg states of atoms are often used because the strong Rydberg-Rydberg interactions can facilitate two-qubit gate operations and simulate many-body systems. However, for most schemes, readout of a Rydberg qubit is a destructive process that precludes its reuse and the application of many error-correcting codes. To address this challenge, we demonstrate a nondestructive implementation of preparation, manipulation, and readout of a single Rydberg qubit embedded in an atomic ensemble with high fidelity. By harnessing the collective optical response of the atomic ensemble, we detect the state of a qubit ~1000x faster than single-atom fluorescence imaging. This method determines the state of the Rydberg qubit without affecting the other atoms in the ensemble to first order, which can then be reused for further operations. With this developed technique, we are making progress towards realizing a quantum computer based on arrays of atomic ensembles, which can significantly improve the computation speed. |
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