Table 1 Qubit parameters and defect statistics.

chip&qubit No.	A_S μm²	l_op μm	l_cov μm	\({\tilde{\rho }}_{{{{\rm{JJ}}}}}\) 1/GHz	\({\tilde{\rho }}_{{{{\rm{surf}}}}}\) 1/GHz	\({\tilde{\rho }}_{0}\) 1/GHz	f₀₁ GHz	T₁ μs
1.1	–	–	–	0.8	28.8	7.7	6.0	10
1.2	12.1	7.1	10.1	19.6	10.0	3.5	6.0	10
1.3	12.7	7.1	19.1	19.6	10.2	3.0	6.2	6
1.4	14.0	15.7	11.1	22.5	24.7	9.7	6.2	8
2.1	–	–	–	2.3	67.7	7.1	5.9	17
2.2	13.1	6.6	10.8	22.4	22.4	3.3	5.8	11
2.3	13.6	6.6	18.4	23.8	23.8	3.9	5.7	12
2.4	14.3	17.2	11.7	25.4	64.9	7.1	5.9	8

Chip 1 contains shadow-junctions made with Dolan bridges, while chip 2 contains cross-type junctions employing intermediate Ar ion milling. A_S denotes the stray junction area. l_op and l_cov are the lengths of the open and covered stray junction edges, respectively. \({\tilde{\rho }}_{{{{\rm{JJ}}}}}\) is the measured spectral density of junction-defects, \({\tilde{\rho }}_{{{{\rm{surf}}}}}\) that of defects on electrode surfaces, and \({\tilde{\rho }}_{0}\) that of unclassified defects. f₀₁ denotes the qubit’s maximum resonance frequency, and T₁ is their average energy relaxation time. The qubit charge energy is E_C = 0.2 GHz ⋅ h, and the Josephson energies E_J are 24 GHz ⋅ h and 21 GHz ⋅ h for samples 1 and 2, respectively. The average vacuum fluctuation strength of the qubit plasma oscillation field is 2.3 kV ⋅ m⁻¹ in the small junction, and 25 V ⋅ m⁻¹ in the stray junction. In total 580 defects were detected on qubit surfaces, and 420 inside the Josephson junctions.

Quick links

Search