Abstract
Trapped-ion (TI) quantum bits are a front-runner technology for quantum computing. TI systems with multiple interconnected traps can overcome the hardware connectivity issue inherent in superconducting qubits and can solve practical problems at scale. With a sufficient number of qubits on the horizon, the multi-programming model for Quantum Computers (QC) has been proposed where multiple users share the same QC for their computing. Multi-programming is enticing for quantum cloud providers as it can maximize device utilization, throughput, and profit for clouds. Users can also benefit from the short wait queue. However, shared access to quantum computers can create new security issues. This paper presents one such vulnerability in shared TI systems that require <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">shuttle</i> operations for communication among traps. Repeated shuttle operations increase quantum bit energy and degrade the reliability of computations (fidelity). We show adversarial program design approaches requiring numerous shuttles. We propose a random and systematic methodology for adversary program generation. Our analysis shows shuttle-exploiting attacks can substantially degrade the fidelities of victim programs by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 2 \times $ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 63 \times $ </tex-math></inline-formula> . Finally, we present several countermeasures such as adopting a hybrid initial mapping policy, padding victim programs with dummy qubits, and capping maximum shuttles.
Highlights
Quantum computing has garnered immense attention from government, industry, and academia alike in recent years It can be advantageous in domains like machine learning [1], drug discovery [2], molecule simulation [3], [4], and optimization [5]
We present an attack in the multiprogramming setting for TI systems by exploiting a new vulnerability in terms of shuttle operations
The shuttle direction policy used in the quantum charge-coupled device (QCCD) compiler [37] is illustrated in Listing 1
Summary
Quantum computing has garnered immense attention from government, industry, and academia alike in recent years It can be advantageous in domains like machine learning [1], drug discovery [2], molecule simulation [3], [4], and optimization [5]. A technology named quantum charge-coupled device (QCCD) is proposed in [36] for scalable and modular trapped-ion systems. Laser pulses are applied in sequence on the ions to manipulate ions’ states to perform computation (quantum gates). The adversary can design his/her program such that it requires computation (gate) between ions from different traps that will need frequent shuttles between traps. BASICS we discuss the basics of trapped-ion quantum computers and terminologies used in the paper. Native 2-qubit gate of trapped-ion systems [48]. A 2-qubit gate cannot be applied to ions from different traps Increasing a chain’s motional mode by repeated shuttles is the basis of the attack proposed in this paper
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