Flicker (1∕f) noise in the critical current of Josephson junctions at 0.09–4.2K

We have measured the low-frequency noise in the critical current Ic of six dc superconducting quantum interference devices (SQUIDs) with resistively shunted Nb–NbOx–PbIn Josephson junctions in the temperature range T=0.09–4.2K. Each device is voltage biased, the applied flux is an integer number of flux quanta, and the current fluctuations are measured with a second dc SQUID. At low frequencies f, there is a component of the power spectrum of the critical current fluctuations given approximately by SIc(f)=CIc2T2∕Af, where A is the area of both junctions, and C≈(3.9±0.4)×10−23m2∕K2. For quantum bits based on Josephson junctions, the scaling of SIc(f) with T2 implies that the dephasing time limited by critical current l∕f noise should scale as 1∕T for temperatures down to at least 0.09K.

[1]  A. Leggett Quantum Mechanics at the Macroscopic Level , 1986 .

[2]  I. Chuang,et al.  Quantum Computation and Quantum Information: Introduction to the Tenth Anniversary Edition , 2010 .

[3]  J. J. Kingston,et al.  Magnetic flux noise in copper oxide superconductors , 1994 .

[4]  T. Duty,et al.  Coherent dynamics of a Josephson charge qubit , 2003, cond-mat/0305433.

[5]  Yu. A. Pashkin,et al.  Quantum oscillations in two coupled charge qubits , 2002, Nature.

[6]  John Clarke,et al.  Flicker (1/f) noise in tunnel junction dc SQUIDS , 1983 .

[7]  Robert A. Buhrman,et al.  Composition of 1/f noise in metal-insulator-metal tunnel junctions , 1984 .

[8]  J. E. Mooij,et al.  Coherent Quantum Dynamics of a Superconducting Flux Qubit , 2003, Science.

[9]  Wakai,et al.  Direct lifetime measurements and interactions of charged defect states in submicron Josephson junctions. , 1987, Physical review letters.

[10]  F. Wellstood,et al.  Temperature dependence of low-frequency noise in AlAl2O3Al single-electron transistors , 2000 .

[11]  John M. Martinis,et al.  Decoherence of a superconducting qubit due to bias noise , 2003 .

[12]  Rogers,et al.  Nature of single-localized-electron states derived from tunneling measurements. , 1985, Physical review letters.

[13]  P. Joyez,et al.  Manipulating the Quantum State of an Electrical Circuit , 2002, Science.

[14]  Low-frequency noise and discrete charge trapping in small-area tunnel junction dc SQUID's , 1986 .

[15]  Roberto Ramos,et al.  Entangled Macroscopic Quantum States in Two Superconducting Qubits , 2003, Science.

[16]  John Clarke,et al.  Low‐frequency excess noise in Nb‐Al2O3‐Nb Josephson tunnel junctions , 1987 .

[17]  John Clarke,et al.  High-Tc super conducting quantum interference devices with slots or holes: Low 1/f noise in ambient magnetic fields , 1997 .

[18]  Vittorio Foglietti,et al.  Low-frequency noise in low 1/f noise dc SQUID's , 1986 .

[19]  J. Clarke,et al.  Excess noise in dc SQUIDs from 4.2K to 0.022K , 1987 .

[20]  Siyuan Han,et al.  Coherent Temporal Oscillations of Macroscopic Quantum States in a Josephson Junction , 2002, Science.

[21]  Vijay Patel,et al.  Quantum superposition of distinct macroscopic states , 2000, Nature.

[22]  J. Martinis,et al.  Rabi oscillations in a large Josephson-junction qubit. , 2002, Physical review letters.