We reported one year ago about the successful research conducted in the ML4Q groups of Simon Trebst, Alex Altland and David DiVincenzo which analyzed cutting edge device structures to demonstrate that some of them are indeed operating dangerously close to a threshold of chaotic meltdown. In a new preprint entitled “Classical Chaos in Quantum Computers” the authors team continues the joint effort, this time addressing the challenge that 50-100 qubit computers already operate outside the range of quantum simulation on silicon computers.

In the paper the authors demonstrate that the simulation of classical limits can be a potent diagnostic tool potentially mitigating this problem. As a testbed for their approach the authors consider the transmon qubit processor, a computing platform in which the coupling of large numbers of nonlinear quantum oscillators may trigger destabilizing chaotic resonances. They find that classical and quantum simulations lead to similar stability metrics (classical Lyapunov exponents vs. quantum wave function participation ratios) in systems with O(10) transmons. However, the big advantage of classical simulation is that it can be pushed to large systems comprising up to thousands of qubits. They exhibit the utility of this classical toolbox by simulating all current IBM transmon chips, including the recently announced 433-qubit processor of the Osprey generation, as well as future devices with 1,121 qubits (Condor generation). For realistic system parameters, they report a systematic increase of Lyapunov exponents in system size, suggesting that larger layouts require added efforts in information protection.

Publication: Classical Chaos in Quantum Computers. Simon-Dominik Börner, Christoph Berke, David P. DiVincenzo, Simon Trebst, Alexander Altland. https://doi.org/10.48550/arXiv.2304.14435 and https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.6.033128

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