Bulletin of the American Physical Society
2020 Annual Meeting of the APS Four Corners Section (Virtual)
Volume 65, Number 16
Friday–Saturday, October 23–24, 2020; Albuquerque, NM (Virtual)
Session E02: Quantum Information ILive
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Chair: Zhexuan Gong, Colorado School of Mines |
Friday, October 23, 2020 2:00PM - 2:24PM Live |
E02.00001: Entanglement dynamics for quantum systems with strongly long-range interactions Invited Speaker: Zhexuan Gong Strongly long-range interacting quantum systems—those with interactions decaying slower than 1/r^D in the distance r on a D-dimensional lattice —have received significant interest in recent years. They are present in leading experimental platforms for quantum computation and simulation, as well as in theoretical models of quantum information scrambling and fast entanglement creation. Since no notion of locality is expected in such systems, a general understanding of their dynamics is lacking. In a step towards rectifying this problem, we prove new Lieb-Robinson-type bounds that constrain the time it takes to entangle two parts of a quantum system with strongly long-range interactions. These bounds are optimal in a variety of physical scenarios where we can construct explicit Hamiltonians that saturate the bounds. [Preview Abstract] |
Friday, October 23, 2020 2:24PM - 2:36PM Live |
E02.00002: Quantum measurement-based feedback simulation of complex dynamics of mean-field $p$-spin models. Manuel Munoz-Arias, Pablo Poggi, Poul Jessen, Ivan Deutsch We study a method for simulating the nonlinear dynamics of many-body spin systems based on measurement-based feedback. We focus on $p$-spin models describing an Ising-like model on a completely connected graph with $p$-body interactions. These models exhibit diverse critical phenomena. For $p=2$ this recovers the Lipkin-Meshkov-Glick (LMG) model, exhibiting a continuous second-order phase transition between paramagnetic and ferromagnetic phases. For $p>2$, the phase transition is a first order and discontinuous. Our protocol considers the collective spin of an ensemble on $N$ qubits, and approximates the dynamics by weakly measuring one projection of the collective spin, followed by unitary evolution conditioned on the measurement outcome~\footnote{Munoz-Arias, et. al, PRL 124, 110503 (2020)}~\footnote{Munoz-Arias, et. al, PRA 102, 022610 (2020)}. We use our scheme to simulate dynamical quantum phase transitions of $p$-spin models, and explore a possible experimental implementation of these dynamical quantum simulations on an atom-light interface. [Preview Abstract] |
Friday, October 23, 2020 2:36PM - 2:48PM Live |
E02.00003: Quantum Phase Estimation Algorithm on Heisenberg-Type Hamiltonians and Possible Optimizations Scott Johnstun, Jean-Francois Van Huele The Quantum Phase Estimation Algorithm is an algorithm of fundamental importance in quantum computation. It can be used to break RSA encryption, perform efficient database searches, and simulate quantum Hamiltonians. We review the algorithm as well as two optimizations based on circular statistics and iterative methods to improve its performance on quantum computers. We then choose a Heisenberg Hamiltonian and use it to demonstrate these optimizations through simulations and experiments on publicly available IBM quantum computers. [Preview Abstract] |
Friday, October 23, 2020 2:48PM - 3:00PM Live |
E02.00004: Quantifying the sensitivity to errors in analog quantum simulation Pablo Poggi, Nathan Lysne, Kevin Kuper, Ivan Deutsch, Poul Jessen Quantum simulators are widely seen as one of the most promising near-term applications of quantum technologies. However, it remains unclear to what extent a noisy device can output reliable results in the presence of unavoidable imperfections. Here we propose a framework to characterize the performance of quantum simulators by linking the robustness of measured quantum expectation values to the spectral properties of the output observable, which in turn can be associated with its macroscopic or microscopic character. We show that, under general assumptions and on average over all states, imperfect devices are able to reproduce the dynamics of macroscopic observables accurately, while the relative error in the expectation value of microscopic observables is much larger on average. We experimentally demonstrate the universality of these features in a state-of-the-art quantum simulator and show that the predicted behavior is generic for a highly accurate device, without assuming any detailed knowledge about the nature of the imperfections. [Preview Abstract] |
Friday, October 23, 2020 3:00PM - 3:12PM Live |
E02.00005: Quantum Teleportation Distance and Qubit Fidelity Bryan Garcia Quantum computing improves on classical computing by using the quantum mechanical principles of superposition and entanglement. In our numerical experiment we investigate the distance dependence of qubit teleportation on a single quantum processor. All computations were performed on the open-access IBM Q platform. The payload qubit is initialized such that state 0 and state 1 are measured with equal probability. We then entangle qubit q[1] with q[2], establishing a link. In our contribution a series of phase transition gates are applied to q[0] to prepare the payload. The entangled pair (q[1] $+$ q[2]) is then entangled with q[0] to create the pathway for teleportation. We will discuss in detail our observed decreasing fidelity of the teleported qubit with increasing teleportation distance. Therefore, this simple quantum computing example shows that error correction is increasingly important with increasing qubit distance, which must be accommodated in the present noisy intermediate-scale quantum era by designing a suitable low-distance qubit network or through algorithmic improvements. [Preview Abstract] |
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