Parameter extraction for a superconducting thermal switch (hTron) SPICE model

Efficiently simulating large circuits is crucial for the broader use of superconducting nanowire-based electronics. However, current simulation tools for this technology are not adapted to the scaling of circuit size and complexity. We focus on the multilayered heater-nanocryotron (hTron), a promising superconducting nanowire-based switch used in applications such as superconducting nanowire single-photon detector (SNSPD) readout. Previously, the hTron was modeled using traditional finite-element methods (FEM), which fall short in simulating systems at a larger scale. An empirical-based method would be better adapted to this task, enhancing both simulation speed and agreement with experimental data. In this work, we perform switching current and activation delay measurements on 17 hTron devices. We then develop a method for extracting physical fitting parameters used to characterize the devices. We build a SPICE behavioral model that reproduces the static and transient device behavior using these parameters, and validate it by comparing its performance to the model developed in a prior work, showing an improvement in simulation time by several orders of magnitude. Our model provides circuit designers with a tool to help understand the hTron's behavior during all design stages, thus promoting broader use of the hTron across various new areas of application.Comment: Supplementary material (LTspice schematics and symbol) available on GitHub: https://github.com/vkaram/hTron-behavioral-mode

Multiplexed control of spin quantum memories in a photonic circuit

A central goal in many quantum information processing applications is a network of quantum memories that can be entangled with each other while being individually controlled and measured with high fidelity. This goal has motivated the development of programmable photonic integrated circuits (PICs) with integrated spin quantum memories using diamond color center spin-photon interfaces. However, this approach introduces a challenge in the microwave control of individual spins within closely packed registers. Here, we present a quantum-memory-integrated photonics platform capable of (i) the integration of multiple diamond color center spins into a cryogenically compatible, high-speed programmable PIC platform; (ii) selective manipulation of individual spin qubits addressed via tunable magnetic field gradients; and (iii) simultaneous control of multiple qubits using numerically optimized microwave pulse shaping. The combination of localized optical control, enabled by the PIC platform, together with selective spin manipulation opens the path to scalable quantum networks on intra-chip and inter-chip platforms.Comment: 10 pages, 4 figure

Efficient simulation of Large-Scale Superconducting Nanowire Circuits

As the size of superconducting nanowire devices increases and the influence of second-order effects, such as thermal or electrostatic coupling, becomes more significant, the complexity of models required to accurately and efficiently simulate the device’s behavior becomes more challenging. Traditional circuit simulators used for superconducting devices tend to focus on frequency-domain simulation and are not optimized for simulating superconducting nanowire geometries in the time-domain. This thesis presents an integrated simulator environment designed with the goal of simulating superconducting nanowires. The work presented in this thesis introduces: 1. an integrated environment for SPICE software that extends its modeling capabilities optimized for superconducting nanowire devices and accompanying experiments; 2. a simple procedure to measure the stability of circuit models used to present an improved nanowire SPICE model; and 3. an efficient Julia-based simulator optimized for superconducting nanowire devices and nonlinear microwave circuits.M.Eng