Superconducting Latch Qubit for Nondestructive Readout
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Solution Overview
Problem
Existing techniques for reading out the state of qubits in superconducting quantum processors often result in 'readout destruction' and noise coupling, affecting the coherence of other qubits and introducing noise from measurement devices.
Innovation Solution
The implementation of superconducting latch qubits to mediate the coupling between computation qubits and measurement devices, reducing noise coupling and allowing for nondestructive readout by latching the state of computation qubits and amplifying signals for robust measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If direct coupling between computation qubits and measurement devices is used, then readout speed is improved, but noise coupling and readout destruction increase
Solution Approach 1:
The patent introduces a latch qubit as an intermediary component between the computation qubit and the measurement device (dc-SQUID). The latch qubit mediates the coupling by latching the state of the computation qubit and transferring it to the measurement device, thereby preventing direct noise coupling and readout destruction while maintaining readout functionality.
2Speed
If direct coupling between computation qubits and measurement devices is used, then readout speed is improved, but coherence of other qubits deteriorates
Solution Approach 1:
The latch qubit serves as a mediator that isolates the computation qubits from the measurement device. By latching the state and transferring it through the intermediary, the system prevents disturbance to the coherence of other qubits while enabling fast readout of the measured qubit.
3Object-affected harmful factors
If latch qubits are used to mediate coupling, then noise coupling is reduced, but device complexity increases
Solution Approach 1:
The readout system is segmented into distinct functional components: computation qubits, latch qubits, and measurement devices. This segmentation allows the latch qubit to perform the specific function of state latching and noise isolation, reducing overall system complexity by dividing responsibilities among specialized components.
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 reduces the impact of readout operations on the quantum processor's coherence and enhances signal robustness against noise, enabling more accurate and isolated state measurement of qubits.
Implementation Method 1
The latch qubit and the magnetometer are inductively coupled
Implementation Method 2
measuring a signal from the latch qubit with the magnetometer
Implementation Method 3
latching the state of computation qubits and amplifying signals for robust measurement
Implementation Method 4
Each of the latch qubits, the computation qubits, and the coupling devices may include one or more Josephson junctions
Implementation Method 5
The coupling devices may include one or more Josephson junctions
Implementation Method 6
Each of the latch qubits, the computation qubits, and the coupling devices may include one or more Josephson junctions
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A superconducting readout system includes a computation qubit; a measurement device to measure a state of the computation qubit; and a latch qubit that mediates communicative coupling between the computation qubit and the measurement device. The latch qubit includes a qubit loop that includes at least two superconducting inductors coupled in series with each other; a compound Josephson junction that interrupts the qubit loop that includes at least two Josephson junctions coupled in series with each other in the compound Josephson junction and coupled in parallel with each other with respect to the qubit loop; and a first clock signal input structure to couple clock signals to the compound Josephson unction.