Quantum Voltage States – VOLTANGLE

Why is it so difficult to obtain a robust qubit? One with a long coherence time, enabling engineers to move beyond research and development and build working quantum computers? Classical bits are immune to noise below a certain threshold, corresponding to the energy to physically flip between 0 and 1. Quantum bits, on the other hand, will start dephasing as soon as there are fluctuations. Many strategies to reduce noise, either passively or actively, are currently being investigated to address the challenge of making resilient quantum bits. Voltangle seeks to exploit quantum synchronization to reduce decoherence in a superconducting qubit.

Huygens first observed phase locking in the oscillation of two pendulums suspended on a wall. Josephson junctions, which obey the same equations in the classical limit, can also be synchronized to each other or to an external microwave drive, resulting in a phenomenon called Shapiro steps. Remarkably, the quantum limit of Shapiro steps is unknown. Voltangle proposes experiments on quantum circuits to demonstrate synchronization to an external, precisely defined microwave drive: the first observation of quantum Shapiro steps. Synchronization results in a degenerate ground state, potentially immune to noise. The computational basis is formed of quantum voltage states, superpositions of two distinct and opposite voltages, locked to the microwave drive frequency with parts-per-trillion accuracy. Studying these "tangled" voltage states may not only lead to better qubits, but will also answer major open questions in nonlinear quantum dynamics and enable observation of a variety of intriguing phenomena including Floquet flatbands and Super Bloch oscillations.