SQUID-arrays coupled to on-chip integrated thin-film superconducting input coils operating coherently

Recently, Superconducting Quantum Interference Device (SQUID) arrays operating in a coherent voltage-modulation state at 77 K showed flux-noise 10 times lower than that of single-SQUIDs similar temperatures. To exploit the superiority SQUID-arrays applications, however, it is essential to preserve state, while magnetic field be measured, Bz, highly inhomogeneous along array as being generated by thin film integrated superconducting input coils or flux-transformers located close proximity. Indeed, flux coupled each individual SQUID may vary significantly array, leading rapid degradation coherency. Here, we present several solutions avoid based on methodology developed assess efficiency signal coupling maintaining state. As proof concept, applied YBa2Cu3O7 800/770 inductively on-chip coils. Each directly two focusers, an increase effective area for which derived analytical formula. Consequently, achieved SQUID-like voltage oscillation amplitudes above mV temperature range (75–83) K, noise 0.2 μΦ0/Hz1/2, consistent with ultra-enhanced operation reached. For strongest scheme implemented experimentally, current white SI1/2 = 32 pA/Hz1/2 was measured. This can used coil flux-transformer, resulting SQUID-array-based magnetometer estimated sensitivity 13 fT/Hz1/2.