Capacitively-Shunted Asymmetric DC-SQUID for Active Qubit Reset
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Solution Overview
Problem
Current methods for resetting superconducting qubits are passive and time-consuming, leading to idle time and inefficiency in quantum computations due to the slow decay of excited states to the ground state, and existing readout circuits do not actively participate in the reset process.
Innovation Solution
A tunable asymmetric DC-SQUID device that uses a capacitive shunting mechanism and external magnetic flux tuning to actively reset and read the quantum state of a qubit, allowing for both dispersive readout and reset operations by adjusting the resonator frequency to match or detune from the qubit's resonance frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If passive reset method is used, then device complexity is reduced, but reset speed and productivity deteriorate
Solution Approach 1:
The readout circuit is designed to perform dual functions: qubit state readout and active qubit reset. By making the readout circuit universal, it can initialize qubits to the ground state during readout operations, eliminating the need for separate reset circuitry and achieving fast reset without proportionally increasing device complexity
Solution Approach 2:
The readout circuit serves itself by incorporating reset capability. During the readout process, the circuit automatically resets the qubit to the ground state, allowing the same component to perform both measurement and initialization functions without requiring external intervention or additional dedicated reset hardware
2Measurement precision
If additional readout resonators are used, then readout precision is improved, but device complexity and loss of time increase
Solution Approach 1:
The readout circuit is designed to perform dual functions: qubit state readout and active qubit reset. By making the readout circuit universal, it can initialize qubits to the ground state during readout operations, eliminating the need for separate reset circuitry and achieving fast reset without proportionally increasing device complexity
Solution Approach 2:
The patent combines the readout and reset functions into a single integrated circuit rather than using separate resonators. This merging of functions reduces the total number of components, decreases device complexity, and minimizes the time required for sequential operations while maintaining readout precision through the asymmetric DC-SQUID design
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 solution enables faster and active reset of qubits, reducing idle time and enhancing the speed of quantum computations by forcing the qubit to the ground energy state more quickly than its natural decay time, while also performing readout operations without the need for additional readout resonators.
Implementation Method 1
A superconducting qubit includes a Josephson junction. A Josephson junction is formed by separating two thin-film superconducting metal layers by a non-superconducting material. When the metal in the superconducting layers is caused to become superconducting—e.g. by reducing the temperature of the metal to a specified cryogenic temperature—pairs of electrons can tunnel from one superconducting layer through the non-superconducting layer to the other superconducting layer.
Implementation Method 2
An external magnetic flux is set to a first value and applied to the tunable resonator, wherein a first value of the external magnetic flux causes the tunable resonator to tune to a first frequency
Implementation Method 3
capacitive device shunting a set of asymmetric DC-SQUIDs to form a tunable resonator
Data Source
AI summary
A tunable resonator is formed by shunting a set of asymmetric DC-SQUIDs with a capacitive device. An asymmetric DC-SQUID includes a first Josephson junction and a second Josephson junction, where the critical currents of the first and second Josephson junctions are different. A coupling is formed between the tunable resonator and a qubit such that the capacitively-shunted asymmetric DC-SQUIDs can dispersively read a quantum state of the qubit. An external magnetic flux is set to a first value and applied to the tunable resonator. A first value of the external magnetic flux causes the tunable resonator to tune to a first frequency within a first frequency difference from a resonance frequency of the qubit, the tunable resonator tuning to the first frequency causes active reset of the qubit.