  Squeezed states are an interesting class of quantum states that have numerous
applications. This work presents the design, characterisation, and operation of
a bow-tie optical parametric amplifier (OPA) for squeezed vacuum generation. We
report the high duty cycle operation and long-term stability of the system that
makes it suitable for post-selection based continuous-variable quantum
information protocols, cluster-state quantum computing, quantum metrology, and
potentially gravitational wave detectors. Over a 50 hour continuous operation,
the measured squeezing levels were greater than 10 dB with a duty cycle of
96.6%. Alternatively, in a different mode of operation, the squeezer can also
operate 10 dB below the quantum noise limit over a 12 hour period with no
relocks, with an average squeezing of 11.9 dB. We also measured a maximum
squeezing level of 12.6 dB at 1550 nm. This represents one of the best reported
squeezing results at 1550 nm to date for a bow-tie cavity. We discuss the
design aspects of the experiment that contribute to the overall stability,
reliability, and longevity of the OPA, along with the automated locking schemes
and different modes of operation.
