Reduction of spontaneous emission and thermal photon noise in quantum computing machines using a galvanically grounded filter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current quantum computing architectures face challenges in maintaining qubit coherence due to spontaneous emission and thermal photon noise, which degrade the relaxation and decoherence times of qubits, limiting their operational effectiveness.
Innovation Solution
A galvanically grounded filter is connected to the signal line of a readout resonator in a quantum processor, with a passband matching the readout resonator frequency and a stopband matching the qubit transition frequency, and thermally connected to a cryostat ground, to suppress spontaneous emission and thermal photon noise, thereby protecting qubits from dephasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter is used to block spontaneous emission and thermal photon noise, then qubit coherence time is improved, but device complexity increases
Solution Approach 1:
The filter is divided into multiple resonator sections (first resonator, second resonator, third resonator) with distinct frequency characteristics. Each resonator handles specific frequency ranges, allowing the system to achieve broad-spectrum noise suppression while maintaining manageable complexity through modular design
Solution Approach 2:
The filter structure serves multiple functions simultaneously: it blocks spontaneous emission from qubits, filters thermal photon noise from measurement lines, and provides impedance matching. This multi-functionality reduces the need for separate components, thereby managing device complexity while improving qubit coherence
2Object-affected harmful factors
If the filter is galvanically connected to ground for thermalization, then thermal photon noise is reduced, but impedance matching becomes more difficult
Solution Approach 1:
The filter employs different resonator sections with locally optimized characteristics: the first resonator is designed for blocking spontaneous emission at qubit frequencies, while the second and third resonators are optimized for thermalization at different temperature stages. This local optimization allows galvanic grounding for thermalization while maintaining impedance matching through frequency-selective design
3Object-affected harmful factors
If the filter blocks frequencies close to the qubit transition frequency, then spontaneous emission is reduced, but readout signal transmission is affected
Solution Approach 1:
The filter utilizes frequency parameter differentiation to resolve the contradiction. The first resonator is tuned to block qubit transition frequencies for spontaneous emission suppression, while the second and third resonators are tuned to passband frequencies that allow readout signal transmission. This parameter-based frequency selection enables simultaneous achievement of both goals
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 effectively reduces thermal photon noise and spontaneous emission, enhancing the coherence times of qubits by providing a galvanic and thermal connection that improves cooling efficiency and impedance matching, thus maintaining qubit stability and operational performance.
Implementation Method 1
The maximum possible relaxation time is set by the Purcell effect, i.e. no coupling to defects, quasiparticles, etc.). Further, in circuit QED architectures, the cavity readout rate is inversely proportional to the relaxation time or qubit lifetime (T1) set by the Purcell effect.
Implementation Method 2
galvanically connecting a signal line of the filter to a reference ground in thermal contact to a stage of a cryostat, the galvanic connection further making a thermal connection to an input signal line of the qubit circuit
Implementation Method 3
The filter has a passband including a readout resonator frequency associated with the readout resonator and a first stopband including a qubit transition frequency associated with the qubit circuit
Data Source
AI summary
Protecting qubits of a quantum processor from spontaneous emission and thermal photon noise includes connecting a first port of a filter to a signal line of a readout resonator of a qubit circuit of a quantum processor. The filter has a passband including a readout resonator frequency associated with the readout resonator and a first stopband including a qubit transition frequency associated with the qubit circuit. A second port of the filter is connected to a measurement device. a signal line of the filter is galvanically connected to a reference ground in thermal contact to a stage of a cryostat. The galvanic connection further makes a thermal connection to an input signal line of the qubit circuit.