Quantum Gate Device Using Segmented Josephson Junctions
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Solution Overview
Problem
Quantum gate devices face high operation error rates due to limited coherence time, requiring longer transition times between energy states, which increases processing time and reduces performance.
Innovation Solution
A quantum gate device with a first and second superconducting circuit connected by a connector, featuring a Josephson device group with enhanced Josephson energy, a capacitor, and a magnetic field applier, allowing for high-speed transitions between energy states through modulated resonance frequencies and electromagnetic wave interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the quantum gate device uses conventional transmon circuit with Josephson device and capacitor, then the device can maintain quantum coherence, but the transition time between energy states is too long (100 nanoseconds)
Solution Approach 1:
The quantum gate device is segmented into multiple independent Josephson devices (first Josephson device and second Josephson device group with n devices) connected in series within a superconducting loop. This segmentation allows the total Josephson energy to be distributed across multiple devices, enabling faster transitions while maintaining the quantum coherence properties through the collective behavior of the segmented Josephson junctions.
Solution Approach 2:
The invention uses a composite structure combining multiple Josephson devices with different Josephson energy characteristics. The first Josephson device has Josephson energy Ej1, while each device in the second group has Josephson energy greater than n×Ej1. This composite arrangement of Josephson devices with specific energy ratios creates the desired resonance frequency modulation capability for high-speed transitions.
2Productivity
If the operation time is extended to maintain coherence, then quantum errors increase, but shortening operation time reduces coherence maintenance capability
Solution Approach 1:
The quantum gate device employs dynamic control of resonance frequencies through the application of magnetic fields. By dynamically adjusting the magnetic flux through the superconducting loop, the resonance frequency can be modulated to match the energy difference between quantum states, enabling fast transitions (16 nanoseconds) while maintaining coherence. This dynamic frequency tuning allows precise control of transition timing and duration.
Solution Approach 2:
The invention changes the magnetic field parameter applied to the superconducting loop to control the Josephson energy and resonance frequency. By varying the magnetic flux parameter, the device can rapidly transition between energy states with controlled timing. This parameter change approach enables the transition time to be reduced from 100 nanoseconds to 16 nanoseconds while maintaining quantum coherence and reducing error rates.
3Loss of time
If electromagnetic wave irradiation is used to induce transitions between energy states, then state changes can be achieved, but the transition time is insufficiently short
Solution Approach 1:
The superconducting loop structure serves multiple functions: it provides the quantum resonant circuit for energy state transitions, acts as a flux sensor for detecting magnetic field changes, and functions as a coupling element for electromagnetic wave interaction. This multi-functionality allows the same structure to enable both the electromagnetic wave-induced transitions and the fast switching capability, achieving 16 nanosecond transition times.
Solution Approach 2:
The magnetic field acts as an intermediary between the control system and the quantum states. By applying magnetic flux through the superconducting loop, the Josephson energy is modulated, which in turn controls the resonance frequency and enables fast transitions between energy states. This intermediary magnetic field mechanism allows precise and rapid control of quantum state transitions without directly perturbing the quantum system.
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 device achieves faster state transitions, reducing error rates and improving quantum computer performance by shortening the time required for energy state changes from approximately 100 nanoseconds to 16 nanoseconds.
Implementation Method 1
When the quantum gate device is cooled to a temperature at which the superconductors in the Josephson device and the line make a transition to a superconducting state, an electric current due to the Josephson effect flows within the transmon, passing through the Josephson device.
Implementation Method 2
This makes the transmon function as a resonance circuit. Due to quantum mechanical effects, this resonance circuit takes one of a plurality of discretized energy states.
Implementation Method 3
An electromagnetic wave whose energy level corresponds to the smallest interval is injected into the Josephson device. This enables the transmon to selectively take only two energy states
Data Source
AI summary
A quantum gate device includes a first superconducting circuit which resonates at a first resonance frequency, second superconducting circuit which resonates at a second resonance frequency, and connector which connects these circuits. The first superconducting circuit includes a single first Josephson device, second Josephson device group, and first capacitor. The second Josephson device group includes n Josephson devices connected by a line made of a superconductor. The Josephson energy possessed by each of the n Josephson devices is greater than n times that of the first Josephson device. The quantum gate device further includes a magnetic field applier which applies a static magnetic field to the partial superconducting circuit, and an electromagnetic wave irradiator (first electromagnetic wave irradiator) which irradiates the first superconducting circuit and/or second superconducting circuit with an electromagnetic wave having a difference frequency which is equal to the difference between the first and second resonance frequencies.