Twisted Superconducting Quantum Diodes Achieve 27.6% Efficiency, Enhancing Anharmonicity and Fidelity

The pursuit of stable, low-power quantum circuits faces a significant hurdle in managing energy loss and unwanted signal reflections, issues that degrade performance and limit scalability. Han Zhong from University of Florida, Denis Kochan from National Cheng Kung University, Igor Zutic from State University of New York at Buffalo, and Yingying Wu demonstrate a novel approach to this problem by creating a quantum diode using twisted layers of a superconducting material. This innovative device, which directs electrical current in a single direction, achieves 27. 6 percent efficiency with only a one-degree twist, and importantly, the team’s quantum simulations reveal that this intermediate level of efficiency actually enhances the stability of quantum information. These findings challenge the conventional wisdom that maximum rectification is always desirable, and establish a new design principle for building more robust and efficient quantum circuits based on twisted superconductors.

Twisted Niobium Diselenide Creates Superconducting Diode

Scientists have engineered a high-performance superconducting diode using twisted bilayers of niobium diselenide (NbSe2). This device exhibits a significant diode effect, meaning current flows more easily in one direction than the other, a crucial property for advanced electronics. The team achieved this by stacking two layers of NbSe2 with a controlled one-degree twist, creating asymmetry in the material’s electronic structure. Varying the overall thickness of the bilayer allowed researchers to investigate how this impacts performance, and experiments demonstrate a clear diode effect with a substantial difference in critical current depending on the direction of flow.

Researchers attribute this behavior to the breaking of symmetry and the creation of a unique superconducting state due to the twisting of the layers, effectively controlling the flow of current. Quantum circuit simulations modeled the device, demonstrating its potential for use in quantum circuits and exploring the impact of noise on performance. The achieved diode efficiency is competitive with other two-dimensional layered systems, demonstrating a promising pathway towards creating high-performance superconducting diodes for both classical and quantum electronics.

Twisted Niobium Diselenide Enables Quantum Diode

Scientists have achieved a significant breakthrough in quantum circuit design by realizing a functional quantum diode in twisted bilayers of niobium diselenide (NbSe2). This device exhibits non-reciprocal transport, meaning current flows more easily in one direction than the other, a crucial property for building advanced quantum technologies. The research demonstrates that a mere one-degree twist between the NbSe2 layers enhances performance, yielding a 27. 6 percent improvement in efficiency over pristine devices. Experiments reveal a finite intrinsic anisotropy within the device, even under extremely weak magnetic fields.

Measurements of critical currents and diode efficiency demonstrate a strong dependence on applied magnetic fields, with maximum rectification efficiency reaching 24. 0 percent at an in-plane field of -100 Oe and 27. 6 percent at -13 Oe with an out-of-plane field. These results indicate that twisting the layers creates asymmetry, impacting the height of surface barriers and influencing the onset of resistive states depending on current polarity. Investigations into the thickness dependence of this effect show that a 16nm device exhibits the most pronounced magnetic field-dependent diode efficiency, while 30nm and 60nm devices display weaker non-reciprocal behavior, highlighting the role of interlayer coupling and symmetry breaking in controlling rectification.

Moderate Rectification Stabilises Qubit Operation

This research demonstrates a new principle for optimising quantum circuit performance through the implementation of quantum diodes, devices that allow directional current flow. Contrary to the conventional drive to maximise diode efficiency, the team reveals that moderate rectification, achieved with a 27. 6 percent efficient twisted bilayer device, is sufficient to stabilise a two-level system crucial for reliable qubit operation. This level of nonreciprocity effectively suppresses backscattering and decoherence, enabling high-fidelity quantum state transport and offering a pathway to low-power quantum circuits.

The findings also highlight the compatibility of these quantum diodes with transmon qubits, a widely used architecture in quantum computing, potentially enhancing their coherence and control fidelity. Furthermore, the researchers suggest the possibility of designing diodes where qubit states define discrete conduction states, opening avenues for novel quantum information storage and processing functionalities. While acknowledging the complexity of materials discovery, the team indicates ongoing exploration of machine learning techniques to accelerate the identification and optimisation of suitable materials for future quantum diode fabrication and integration into practical quantum circuits.