Multi-Cavity Quantum Gates Using Transmon-Mediated Coupling
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Solution Overview
Problem
Conventional quantum information processing with superconducting circuits faces limitations in coherence times and fidelity of quantum operations due to transmon decoherence, especially during cavity-transmon coupling, which affects the scalability and accuracy of quantum error correction and gate operations.
Innovation Solution
A multi-cavity quantum information system is developed where quantum information is stored in microwave photon states within high-Q resonators, with transmons acting as ancillae for universal quantum control and error correction, utilizing beam splitter and controlled phase shift operations to implement universal quantum logic gates, including c-SWAP and e-SWAP gates, to enhance coherence and fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If transmons are used for quantum control and error correction, then quantum operation capability is improved, but coherence times deteriorate due to transmon decoherence
Solution Approach 1:
The patent introduces an intermediary coupling mechanism between transmons and cavities that mediates the interaction while protecting the cavity quantum states from direct exposure to transmon decoherence. The coupling allows transmons to perform control operations on cavity-encoded qubits without the cavity states directly experiencing the transmon's decoherence, thus extending effective coherence times while maintaining quantum control capability.
2Measurement precision
If cavity-transmon coupling is strengthened for better control, then quantum gate fidelity is improved, but transmon decoherence increases
Solution Approach 1:
The patent segments the quantum system into distinct functional components: cavity modes that store quantum information with long coherence times, and transmons that provide controllable interactions. This segmentation allows the system to achieve high gate fidelity through controlled coupling while isolating the information-bearing cavity states from the decoherence-prone transmons, thereby maintaining transmon stability.
3Force
If conventional superconducting qubits are used, then strong coupling and simple two-qubit gates are achieved, but scalability and coherence times are limited
Solution Approach 1:
The patent implements a universal quantum bus architecture where a single cavity mode can mediate interactions between multiple transmons simultaneously. This multi-functional coupling mechanism enables the system to scale to many qubits while maintaining strong effective coupling strengths, as the cavity bus can facilitate two-qubit gates between any pair of connected transmons without requiring direct pairwise coupling between all qubit pairs.
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 extends coherence times, improves the fidelity of quantum operations, and enables scalable and robust quantum error correction, allowing for universal quantum computation and flexible encoding schemes independent of the logical encoding used.
Implementation Method 1
All superconducting qubit designs use at least one Josephson junction as a non-linear non-dissipative element
Implementation Method 2
quantum information is stored in microwave photon states within high-Q resonators
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3A~3C
AI summary
Techniques for implementing robust quantum logic gates are provided and described. In some aspects, a quantum logic gate between a plurality of cavities comprising a first cavity and a second cavity is implemented by performing a first beam splitter operation between the first cavity and the second cavity using a coupling transmon that is dispersively coupled to both the first cavity and the second cavity, and performing a controlled phase shift operation between the second cavity and an ancilla transmon that is dispersively coupled to the second cavity but not dispersively coupled to the first cavity.