Figure 
shows the block diagram of the experiment. Physical
layout of the RSFQ chip is shown in Fig. . We used an
updated version of the room-temperature data acquisition system
described in [17] and specifically designed for the
analog-to-digital converter experiment [27]. This
interface had certain features which are not required for the
accumulation of the autocorrelator output: data read-out was
triggered by the clock signal and results were stored in a sequential
manner inside the FIFO register as 4096 16-bit numbers. When FIFO was
full the clock signal was disabled and contents of the FIFO were
unloaded to the computer memory. At 
speed of the on-chip
clock and 
speed of the downscaled output clock, FIFO was
full every 
. It took our i486 computer more than 
to
process data from FIFO, so most of the autocorrelator output was
lost. A specialized room-temperature data acquisition system for
accumulation of the autocorrelator data is currently being designed.
Figure: Block diagram of the high-speed experiment.
Figure: Layout of the 16-channel autocorrelator. Total
number of Josephson junctions: 1636.