Tunable Coupling Qubit Architecture for Superconducting Qubit Gates
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Solution Overview
Problem
Current superconducting qubit gates face limitations in coherence time due to 1/f noise for tunable frequency qubits and have low on/off ratios and addressability issues for microwave-driven qubits, while geometric phase gates are slow and hard to implement.
Innovation Solution
A multi-qubit tunable coupling architecture using fixed-frequency transmon qubits and a frequency-tunable ancilla qubit that modulates coupling strength through magnetic flux, enabling efficient two-qubit interactions with improved coherence and addressability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tunable frequency qubits are used to activate resonant interaction for two-qubit gates, then the on-off ratio is improved, but coherence time is reduced due to 1/f noise
Solution Approach 1:
The system separates the qubit frequency from the coupling mechanism. Fixed-frequency qubits maintain long coherence times while a separate tunable coupling element (Josephson junction or SQUID) provides the on-off ratio control. This segmentation allows each component to optimize its function independently.
Solution Approach 2:
A tunable coupling element acts as an intermediary between fixed-frequency qubits to activate interactions. This mediator enables resonant coupling control without requiring the qubits themselves to be tunable, thus preserving their coherence while achieving high on-off ratios.
2Duration of action of stationary object
If fixed-frequency qubits are used to be immune to flux noise, then coherence time is improved, but addressability and on/off ratio are reduced for microwave-driven gates
Solution Approach 1:
The tunable coupling element serves as an intermediary that enables selective addressing of fixed-frequency qubits. By tuning the coupling element's frequency, specific qubit pairs can be activated for interactions while others remain isolated, providing both long-range coupling and precise addressability.
Solution Approach 2:
The system changes the frequency parameter of the coupling element rather than the qubits themselves. This allows dynamic control of which qubit pairs interact by matching the coupling element frequency to the desired interaction frequency, enabling selective addressing without compromising qubit coherence.
3Object-affected harmful factors
If microwave pulses are used to activate gates in fixed-frequency qubits, then flux noise immunity is improved, but unwanted interactions and low on/off ratio occur
Solution Approach 1:
The tunable coupling element acts as a frequency-selective mediator that enables controlled interactions between fixed-frequency qubits. By tuning the coupling element to match specific qubit transition frequencies, desired interactions are activated while unwanted interactions remain suppressed, achieving high on-off ratios without flux noise.
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
This approach allows for scalable quantum computation and simulation by enhancing coherence times, improving on/off ratios, and enabling fast and addressable two-qubit gates with reduced noise resilience, facilitating universal quantum computing and simulation.
Implementation Method 1
a tunable coupling qubit that activates an interaction between the two qubits by modulation of a frequency of the tunable coupling qubit
Implementation Method 2
Each qubit is a transmon-type qubit and the tunable coupling qubit is a transmon-type qubit with an additional Josephson junction forming a superconducting quantum interference device (SQUID) loop
Data Source
AI summary
Various embodiments provide a coupling mechanism, method of activation and a square lattice. The coupling mechanism comprises two qubits and a tunable coupling qubit that activates an interaction between the two qubits by modulation of a frequency of the tunable coupling qubit. The tunable coupling qubit capacitively couples the two qubits. The tunable coupling qubit is modulated at a difference frequency of the two qubits. The difference frequency may be significantly larger than an anharmonicity of the two qubits. The tunable coupling qubit may be coupled to the two qubits by two electrodes separated by a superconducting quantum interference device (SQUID) loop having two Josephson junctions or by a single electrode with a SQUID loop coupling to ground. The SQUID loop is controlled by an inductively-coupled flux bias line positioned at the center of the tunable coupling qubit.