Tunable Quantum Coupler With Capacitive Cancellation for ZZ Error Control
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Solution Overview
Problem
In quantum computing, nearest neighbor qubits coupled for quantum gates experience unintentional coherent rotations and ZZ errors, leading to gate errors and performance limitations due to the always-on coupling, which existing tunable couplers with resonant frequencies above qubits cannot effectively mitigate for a broad range of detuning.
Innovation Solution
A quantum coupler device comprising a tunable coupler and a capacitor device, where the capacitor provides a coupling opposite in sign to the tunable coupler, allowing for control of qubit interactions to eliminate coherent rotations and errors by tuning the resonant frequency to match or exceed that of the qubits, thereby reducing gate errors and increasing operation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tunable coupler with resonant frequency above qubits is used, then coherent rotations and ZZ errors are reduced, but gate speed becomes slow and gate performance deteriorates for broad detuning ranges
Solution Approach 1:
The patent implements a dynamically tunable coupler where the resonant frequency can be adjusted in real-time. By tuning the coupler's resonant frequency to match the qubit frequency during gate operations, the system achieves both high gate speed and effective suppression of coherent rotations. The dynamic adjustment allows the coupler to adapt between different operational modes (fast gate vs. error suppression) as needed.
Solution Approach 2:
The patent changes the resonant frequency parameter of the coupler from a fixed value above qubit frequency to a tunable parameter that can match qubit frequency. This parameter change enables the coupler to operate at resonance with qubits during gate operations, significantly enhancing coupling strength and gate speed while maintaining the ability to suppress coherent rotations when detuned.
2Productivity
If coupling between nearest neighbor qubits is always on, then quantum gate operations can be performed, but unintentional coherent rotations and ZZ errors occur on spectator qubits
Solution Approach 1:
The patent introduces a tunable coupler as an intermediary element between qubits. This coupler mediates the interaction between qubits during gate operations, enabling controlled coupling when needed while preventing unwanted direct coupling between spectator qubits. The coupler acts as a gatekeeper that regulates quantum interactions, allowing productive operations while suppressing harmful coherent rotations on non-participating qubits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces quantum gate errors, increases the speed of quantum operations, and improves the performance and fidelity of quantum processors by selectively turning off coupling between qubits to prevent coherent rotations and errors.
Implementation Method 1
a capacitor device coupled to terminals of an opposite polarity of the first qubit and the second qubit, the capacitor device configured to provide a second coupling that is opposite in sign relative to the first coupling
Data Source
AI summary
Devices and/or computer-implemented methods to facilitate a quantum gate between qubits using a tunable coupler and a capacitor device are provided. According to an embodiment, a quantum coupler device can comprise a tunable coupler coupled between terminals of a same polarity of a first qubit and a second qubit, the tunable coupler configured to control a first coupling between the first qubit and the second qubit. The quantum coupler device can further comprise a capacitor device coupled to terminals of an opposite polarity of the first qubit and the second qubit, the capacitor device configured to provide a second coupling that is opposite in sign relative to the first coupling.