The observation of the gate-controlled supercurrent (GCS) effect in superconducting nanostructures initiated major research efforts toward the realisation of superconducting-based computing architectures. Here we introduce a universal logic circuit that can be a promising superconducting building block of classical hybrid supercomputers. We demonstrate a functionally complete set of logic gates by realising the AND, OR, NOT and COPY gates. The general layout and scalability of our device, combined with recent experiments demonstrating fast switching and small voltage signals, make it a functional candidate in superconducting electronics. Our device enables the realization of all classical logic gates and the half-adder combinational logic circuit using at most three nanowires, each uniquely configured with two side-gate electrodes.
The observation of the gate-controlled supercurrent (GCS) effect in superconducting nanostructures initiated major research efforts toward the realisation of superconducting-based computing architectures. Here we introduce a universal logic circuit that can be a promising superconducting building block of classical hybrid supercomputers. We demonstrate a functionally complete set of logic gates by realising the AND, OR, NOT and COPY gates. The general layout and scalability of our device, combined with recent experiments demonstrating fast switching and small voltage signals, make it a functional candidate in superconducting electronics. Our device enables the realization of all classical logic gates and the half-adder combinational logic circuit using at most three nanowires, each uniquely configured with two side-gate electrodes.
The growing demand for ultra low power computing and the emergence of quantum technologies have intensified interest in cryogenic electronics, particularly superconducting devices. Despite their promise, current controlled superconducting components face fundamental challenges in cascadability, limiting their effectiveness in complex logic architectures. To overcome this, recent efforts have focused on developing gate tunable superconducting devices, such as Josephson junction field effect transistors (JJFETs). However, achieving robust control and sufficient supercurrent gain, both critical for transistor-like performance in logic circuits remains a key challenge. A recent advancement in JJFET design, based on InAs and GaSb heterostructures, demonstrates enhanced gain and favorable device characteristics suitable for circuit integration. Building on this innovation, we propose and analyze fundamental voltage controlled logic topologies using the quantum enhanced JJFET. We develop a Verilog A based circuit compatible compact model of the quantum enhanced JJFET which accurately captures the experimentally observed device characteristics. To ensure cascadability, our logic circuits incorporate the multilayered Heater Nanocryotron (nTron), a superconducting nanowire-based thermal switch. Through simulation based analysis, we demonstrate the successful implementation of fundamental logic gates, including NOT, NAND, and NOR. Furthermore, we design a 3 input majority gate, which plays a pivotal role in quantum and reversible computing due to its universality. Finally, to demonstrate the cascadability of our proposed logic topology, we demonstrate the operation of a 2 input XOR gate based on our designed JJFET based NOT, NAND, and NOR gate.
The development of superconducting electronics based on nanocryotrons has been limited so far to few device circuits, in part due to the lack of standard and robust logic cells. Here, we introduce and experimentally demonstrate designs for a set of nanocryotron-based building blocks that can be configured and combined to implement memory and logic functions. The devices were fabricated by patterning a single superconducting layer of niobium nitride and measured in liquid helium on a wide range of operating points. The tests show 10 − 4 bit error rates with above ± 20 % margins up to 50 MHz and the possibility of operating under the effect of an out-of-plane 36 mT magnetic field, with ± 30 % margins at 10 MHz. Additionally, we designed and measured an equivalent delay-flip-flop made of two memory cells to show the possibility of combining multiple building blocks to make larger circuits. These blocks may constitute a solid foundation for the development of nanocryotron logic circuits and finite-state machines with potential applications in the integrated processing and control of superconducting nanowire single-photon detectors.
High Resolution Image Download MS PowerPoint Slide Logic circuits consist of devices that can be controlled between two distinct states. The recent demonstration that a superconducting current flowing in a constriction can be controlled via a gate voltage ( V G )─gate-controlled supercurrent (GCS)─can lead to superconducting logic with better performance than existing logics. However, before such logic is developed, high reproducibility in the functioning of GCS devices and optimization of their performance must be achieved. Here, we report an investigation of gated Nb devices showing GCS with very high reproducibility. Based on the investigation of a statistically significant number of devices, we demonstrate that the GCS is independent of the constriction width, in contrast with previous reports, and confirm a strong correlation between the GCS and the leakage current ( I leak ) induced by V G . We also achieve a voltage output in our devices larger than the typical values reported to date by at least 1 order of magnitude, which is relevant for the future interconnection of devices, and show that I leak can be used as a tool to modulate the operational V G of devices on a SiO 2 substrates. These results altogether represent an important step forward toward the optimization of reproducibility and performance of GCS devices, and the future development of a GCS-based logic.
Superconducting (SC) electronics (SCE) is one of the major requirements to develop a large-scale practical quantum computing system. (Figs. 1(a)) [1]. Currently, a room temperature conventional computer is used as the control processor which requires a huge number of lossy interconnects to connect with the qubits placed at a few millikelvin temperatures. This, in turn, limits the scalability of the quantum computing system up to hundreds of qubits which is not enough to achieve the full potential [2]. Therefore, along with a suitable cryogenic memory, a cryogenic (preferably superconducting) control processor is required to develop a quantum computing system with thousands of qubits. Moreover, SCE offers ultra-fast (hundreds of gigahertz) and highly energy efficient (sub attojoule/bit) performance [3]. Therefore, SCE is projected to achieve the department of energy (DOE) exascale goal which the conventional supercomputers failed to achieve (Fig. 1(b)) [4]. However, Josephson junction-based SC circuits suffer from limited integration density due to flux trapping, difficulty in driving large impedances, fanning out digital signals, and operating in noisy environments [5]. To address these existing issues, here, we present a novel reconfigurable SC logic circuit using a nano-cryotron (nTron) that can perform 1-input copy, 2-input AND and OR, and 3-input majority logic functionalities. This work can enable the implementation of highly scalable and energy-efficient SC processor since the use of only one device. To achieve the reconfigurable nature of the logic circuit, we utilize the multi-gate switching of nTron.
Superconductor nanodevices are widely applied in quantum computers and quantum detectors. Gate-controlled supercurrent (GCS) provides a potential platform for developing quantum systems, but the mechanism remains controversial. Recent reports suggest that there may be out-of-equilibrium phonons acting in GCS, but insightful investigations are lacking. Here, we report an incoherent superconducting nanowire phonon detector to convert the phase transitions induced by out-of-equilibrium phonons into electric pulse signals, enabling discrete-time measurements. The statistical properties of the gate-induced signals reveal the Poisson properties of phonon injection and the thermalization dynamics of hot electrons in the GCS on the α-Si substrate. These mechanisms are further evidenced by applying opposite gate voltages on two remote gates, in which only phonons play a role. The proposed detector not only is a candidate for constructing phonon-based solid quantum devices based on the GCS but also contributes to research on the out-of-equilibrium phenomena in superconducting nanodevices.
It was recently discovered that supercurrents flowing through thin superconducting nanowires can be quenched by applying a gate voltage to a nearby gate electrode. This gate control of supercurrents, known as the GCS effect, could enable superconducting transistor logic. Here, we report that the GCS also manifests in a suppression of Meissner screening, establishing the phenomenon as a genuine feature of superconductivity that is not restricted to transport. Using a scanning nitrogen-vacancy (NV) magnetometer at sub-Kelvin temperatures, we image the nanoscale spatial region of GCS suppression in micron-size niobium islands. Our observations are compatible with a microscopic hot-spot model of quasiparticle generation and diffusion, and in conflict with other candidate mechanisms such as Joule heating or an electric field effect. Our work introduces an alternative means for studying quasiparticle dynamics in superconducting nanostructures, and showcases the power of local imaging techniques for understanding emergent condensed matter phenomena.