Frequency-Modulated Tunable Coupler for Fast Multi-Qubit Entanglement
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Solution Overview
Problem
Superconducting qubits can only store quantum information for a finite coherence time, limiting the preparation of highly entangled multi-qubit states, which is essential for quantum computing and sensing, due to the lengthy process of sequential two-qubit gate operations, thereby restricting the number of qubits that can be used.
Innovation Solution
Modulating the frequency of a tunable coupler at multiple frequencies to drive first-order energy transitions, allowing for simultaneous entanglement of multiple qubits within a short operation time, thereby reducing state preparation time and increasing the number of qubits that can be used in quantum processing devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sequential two-qubit gate operations are used to prepare highly entangled multi-qubit states, then the preparation can be achieved with current technologies, but the preparation time becomes excessively long and consumes a substantial amount of coherence time
Solution Approach 1:
The patent segments the state preparation process into simultaneous independent two-qubit gate operations rather than sequential operations. Multiple CNOT gates are executed in parallel by applying a global microwave pulse that simultaneously drives all coupled qubit pairs, reducing the total preparation time from O(N) sequential steps to O(1) parallel step while maintaining high fidelity through controlled coupling strengths.
Solution Approach 2:
The patent employs periodic microwave pulses with specific frequencies and durations to drive simultaneous two-qubit gate operations. By tuning the pulse frequency to match the qubit transition frequencies and controlling the pulse duration to achieve the desired gate fidelity, the system can execute multiple entangling operations in a single periodic action cycle, dramatically reducing state preparation time while maintaining reliability.
2Quantity of substance
If the number of qubits is increased to enhance quantum computing power, then more complex quantum systems can be simulated, but the state preparation time increases and eventually becomes comparable to the coherence time
Solution Approach 1:
The patent implements a universal coupling mechanism where a single controllable coupling element can simultaneously mediate two-qubit interactions for all qubit pairs in the system. This multi-functional coupling approach allows the same physical mechanism to serve multiple entangling operations in parallel, enabling the system to scale to larger qubit numbers without proportionally increasing state preparation time, as the coupling infrastructure serves the entire qubit array simultaneously.
3Stability of the object's composition
If fixed frequency qubits are used to achieve high coherence, then the qubit stability is improved, but the gate operation speed becomes relatively slow
Solution Approach 1:
The patent introduces a controllable coupling element as an intermediary between fixed-frequency qubits. This mediator enables fast gate operations by providing a controlled interaction pathway that does not require tuning the qubit frequencies themselves. The coupling element can be dynamically adjusted to enable or disable interactions, allowing rapid gate execution while the qubits maintain their high coherence properties through fixed frequency operation.
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 enables high gate rates, achieving entangling operations as fast as single qubit gates, reducing errors, and allowing for the scaling of quantum computers or sensors to a larger number of qubits while maintaining high fidelity.
Implementation Method 1
the frequency of the tunable coupler is modulated at two frequencies. That is, the coupler is, on the one hand, modulated at a first frequency, so as to drive a first transition and thereby transfer (at least partly) an excitation of said one of the quantum circuits to the tunable coupler
Implementation Method 2
Each of the first and second transition(s) is a first-order energy transition
Data Source
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AI summary
Techniques relate to operating a quantum processing device is provided. The device includes at least two fixed- frequency quantum circuits coupled to a frequency-tunable coupler. The frequency of the coupler can be modulated so as to drive at least two selectively addressable energy transitions in the quantum processing device. The method includes modulating the frequency of the coupler so as to drive two first-order energy transitions. This is done so as to transfer (at least partly) an excitation of one of the quantum circuits to at least another one of the quantum circuits, via the tunable coupler. Related quantum processing devices are also provided.