  Operation of a Superconducting Quantum Interference Device (SQUID) made of
stacked Josephson junctions is analyzed numerically for a variety of junction
parameters. Due to a magnetic coupling of junctions in the stack, such a SQUID
has certain advantages as compared to an uncoupled multi-junction SQUID.
Namely, metastability of current-flux modulation can be reduced and a
voltage-flux modulation can be improved if junctions in the stack are
phase-locked. Optimum operation of the SQUID is expected for moderately long,
strongly coupled stacked Josephson junctions. A possibility of making a stacked
Josephson junction SQUID based on intrinsic Josephson junctions in high-Tc
superconductor is discussed.
