Even harmonic Josephson magnetometry

A novel Josephson junction magnetometry scheme is proposed in which magnetic flux is applied to Josephson junctions with a modulation flux +or-z( Phi /sub 0//2 pi ) cos omega t. Two Josephson junctions are used in a push-pull mode to perform amplification through two mechanisms: negative inductance amplification of DC (low frequency) components and parametric amplification of the second harmonic. The second harmonic component of the Josephson currents, which is directly proportional to the strength of the input flux, is then selected and amplified by a phase-sensitive detector. Computer simulations show that the device behaves very well as a magnetic flux sensor with a DC offset free feature. The device´s parameters and noise problems are also discussed. A preliminary analysis indicates that it is likely to have a better sensitivity than superconducting quantum interference devices.<>