We introduce quantum circuits for simulations of multi-mode state-vectors on 3D cQED processors, using matrix product state representations. The circuits are demonstrated as appliedto simulations of molecular docking based on holographic Gaussian boson sampling, as illustrated for binding of a thiol-containing aryl sulfonamide ligand to the tumor necrosis factor-α converting enzyme receptor. We show that cQED devices with a modest number of modes could be employed to simulate multimode systems by re-purposing working modes through measurement and re-initialization. We anticipate a wide range of GBS applications could be implemented on compact 3D cQED processors analogously, using the holographic approach. Simulations on qubit-based quantum computers could be implemented analogously, using circuits that represent continuous variables in terms of truncated expansions of Fock states.
Kerr parametric oscillators are potential building blocks for fault-tolerant quantum computers. They can stabilize Kerr-cat qubits, which offer advantages towards the encoding and manipulationof error-protected quantum information. Kerr-cat qubits have been recently realized with the SNAIL transmon superconducting circuit by combining nonlinearities and a squeezing drive. These superconducting qubits can lead to fast gate times due to their access to large anharmonicities. However, we show that when the nonlinearities are large and the drive strong, chaos sets in and melts the qubit away. We provide an equation for the border between regularity and chaos and determine the regime of validity of the Kerr-cat qubit, beyond which it disintegrates. This is done through the quantum analysis of the quasienergies and Floquet states of the driven system, and is complemented with classical tools that include Poincaré sections and Lyapunov exponents. By identifying the danger zone for parametric quantum computation, we uncover another application for driven superconducting circuits, that of devices to investigate quantum chaos.
The efficient simulation of quantum systems is a primary motivating factor for developing controllable quantum machines. A controllable bosonic machine is naturally suited for simulatingsystems with underlying bosonic structure, exploiting both quantum interference and an intrinsically large Hilbert space. Here, we experimentally realize a bosonic superconducting processor that combines arbitrary state preparation, a complete set of Gaussian operations, plus an essential non-Gaussian resource – a novel single-shot photon number resolving measurement scheme – all in one device. We utilize these controls to simulate the bosonic problem of molecular vibronic spectra, extracting the corresponding Franck-Condon factors for photoelectron processes in H2O, O3, NO2, and SO2. Our results demonstrate the versatile capabilities of the circuit QED platform, which can be extended to include non-Gaussian operations for simulating an even wider class of bosonic systems.