paper / stevengirvin / Apr 20
The paper introduces a normal-ordered Hamiltonian expansion to derive formally exact amplitudes, termed supercoefficients, for arbitrary parametric processes in single-degree-of-freedom driven Josephson circuits like SNAIL and SQUID designs. These supercoefficients encode full circuit topology, nonlinearity, and drive information, enabling strong-drive regime studies with closed-form expressions for stray-inductor-free cases. The framework extends to multi-mode systems, higher-harmonics Josephson models, multi-drive scenarios, and eigenstate bases, demonstrated via Kerr-cat qubit parameter estimation, chaos criteria, and beam-splitter interaction activation.
josephson-circuitsparametric-processessuperconducting-circuitskerr-cat-qubitsquantum-hamiltoniansquid-circuitssnail-circuits
“Formally exact amplitudes (supercoefficients) are obtained for parametric processes in driven SNAIL-based and SQUID-based circuits.”
paper / stevengirvin / Apr 20
In a 1D Z2 lattice gauge theory coupled to soft-core bosons at unit filling, strong electric fields and weak on-site interactions induce a bunching state with superextensive energy and macroscopic particle number fluctuations via gauge-mediated resonant pair hopping. Increasing on-site interactions transitions this to a pair superfluid with finite superfluid density and power-law pair correlations, then to an incompressible pair Mott insulator at large interactions due to gauge-constrained effective interactions. Weak fields yield a plasma phase with balanced even-odd boson occupations and large short-range correlations. These phases, challenging for classical numerics, suit quantum simulation in circuit QED, neutral atoms, and trapped ions.
z2-lattice-gauge-theoryhiggs-modelmany-body-phasesbosonic-matterquantum-simulationphase-diagram
“Pair hopping mediated by gauge fields causes a bunching state with superextensive energy and macroscopic particle number fluctuations at strong electric field strengths and weak on-site interactions.”
paper / stevengirvin / Dec 23
This paper introduces novel numerical techniques for constructing time-dependent Hamiltonian models of microwave-driven superconducting Josephson circuits. These techniques leverage classical microwave simulations, executed in finite element solvers, to accurately capture device dynamics. Unlike previous methods, this approach does not rely on a lumped-element description, allowing for characterization of circuits with arbitrary geometries and complex electromagnetic environments. The methods are crucial for optimizing circuit designs and advancing superconducting quantum computing applications.
quantum-computingjosephson-circuitsmicrowave-driveshamiltonian-modelingsuperconducting-circuitsquantum-systemsnumerical-methods
“Existing numerical methods like black-box quantization (BBQ) and energy-participation ratio (EPR) are insufficient for modeling driven superconducting circuits and do not account for noise and dissipation from microwave ports.”
paper / stevengirvin / Nov 17
This paper reviews the potential of solid-state nuclear clocks utilizing the low-energy 8.4 eV nuclear transition in Thorium-229. The authors discuss the fundamental physics, technological hurdles, and current limitations of atomic clocks, contrasting them with the prospective advantages of a Th-229 based system. Key challenges include mitigating inhomogeneous broadening caused by crystal defects and dopants.
solid-state-physicsnuclear-clocksthorium-229atomic-physicsmaterials-sciencequantum-metrology
“Solid-state nuclear clocks based on Thorium-229 (Th-229) offer a promising alternative to current atomic clock technology.”
paper / stevengirvin / Apr 28
This paper introduces Non-Abelian Quantum Signal Processing (NQSP), an extension of traditional QSP that utilizes non-commuting control parameters for hybrid continuous- and discrete-variable quantum systems. NQSP, specifically through the Gaussian-Controlled-Rotation (GCR) sequence, demonstrates significant speedup and performance comparable to state-of-the-art abelian QSP methods. This development is crucial for robust quantum control, enabling high-fidelity state preparation and error-corrected operations in next-generation quantum computing architectures.
quantum-signal-processingquantum-controlquantum-computingquantum-error-correctionnon-abelian-qsphybrid-quantum-systems
“Non-abelian QSP (NQSP) extends traditional QSP by using non-commuting control parameters.”