Tunable Transmon Qubit Biasing for Frequency Alignment
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Solution Overview
Problem
Current fabrication techniques for quantum circuits result in minor variations in inductance and capacitance, leading to deviations from desired state transition frequencies, making it challenging to control multiple qubits with a single digital-to-analog converter and introducing errors in quantum algorithms.
Innovation Solution
A tunable transmon qubit assembly is designed with a bias circuit that adjusts the frequency of state transitions, allowing multiple qubits to be controlled by a single DAC, using a Josephson junction and DC SQUID structure with a capacitor, and applying a constant bias flux to align frequency curves and correct for deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If current fabrication techniques are used for quantum circuits, then manufacturing simplicity is maintained, but manufacturing precision deteriorates due to minor variations in inductance and capacitance causing deviations from desired state transition frequencies
Solution Approach 1:
The patent applies parameter changes by introducing a tunable inductance element (DC SQUID) that allows the inductance parameter to be adjusted after fabrication. This enables compensation for fabrication variations by changing the operational parameters of the circuit rather than requiring precise fabrication, thus resolving the contradiction between manufacturing precision and ease of manufacture
Solution Approach 2:
The patent implements dynamics by making the inductance tunable through the DC SQUID structure, which allows the circuit to adapt its parameters dynamically. This dynamic adjustment capability enables frequency tuning to compensate for fabrication variations without requiring complex fabrication processes
2Loss of energy
If multiple qubits are controlled by separate digital-to-analog converters, then control precision is maintained, but power dissipation increases significantly
Solution Approach 1:
The patent applies universality by designing a system where a single DAC can control multiple qubits through the shared tunable inductance mechanism. The DC SQUID structure serves multiple functions: it provides inductance, enables tuning, and allows multiplexed control, thus reducing the number of DACs needed while maintaining control precision across multiple qubits
Solution Approach 2:
The patent merges the control functions by combining multiple qubit control paths through a shared DAC and tunable inductance structure. By merging the control architecture and using the DC SQUID as a common tuning element, the system reduces power dissipation from multiple DACs while maintaining individual qubit control precision
3Reliability
If fabrication variations are accepted without correction, then device complexity is reduced, but reliability deteriorates due to errors in quantum algorithms
Solution Approach 1:
The patent implements feedback by measuring the actual state transition frequency of each qubit and using this information to adjust the DC SQUID flux bias accordingly. This feedback loop compensates for fabrication variations, improving quantum algorithm reliability without requiring overly complex circuit structures, as the correction is achieved through controlled flux adjustment
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 precise control of multiple qubits with significant savings in power dissipation, overcoming fabrication limitations and achieving the necessary precision for large-scale integration with local digital control circuitry.
Implementation Method 1
A tunable transmon qubit assembly includes a first Josephson junction on a first path between a transmission line and a circuit ground, second and third Josephson junctions arranged in parallel with one another on a second path between the transmission line and the circuit ground to form a direct current superconducting quantum interference device (DC SQUID) in parallel with the first Josephson junction
Implementation Method 2
A bias circuit is configured to provide a constant bias flux to the DC SQUID to adjust a frequency curve of the transmon qubit assembly
Data Source
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AI summary
Systems and methods are provided for a tunable transmon qubit. The qubit includes a first Josephson junction on a first path between a transmission line and a circuit ground and second and third Josephson junctions arranged in parallel with one another on a second path between the transmission line and the circuit ground to form a direct current superconducting quantum interference device (DC SQUID). The DC SQUID is in parallel with the first Josephson junction. A capacitor is arranged in parallel with the first Josephson junction and the DC SQUID on a third path between the transmission line and the circuit ground as to form, in combination with the first path, an outer loop of the tunable transmon qubit. A bias circuit is configured to provide a constant bias flux to one of the DC SQUID and the outer loop of the tunable transmon qubit.