  It has recently become possible to encode the quantum state of
superconducting qubits and the position of nanomechanical oscillators into the
states of microwave fields. However, to make an ideal measurement of the state
of a qubit, or to detect the position of a mechanical oscillator with
quantum-limited sensitivity requires an amplifier that adds no noise. If an
amplifier adds less than half a quantum of noise, it can also squeeze the
quantum noise of the electromagnetic vacuum. Highly squeezed states of the
vacuum serve as an important quantum information resource. They can be used to
generate entanglement or to realize back-action-evading measurements of
position. Here we introduce a general purpose parametric device, which operates
in a frequency band between 4 and 8 GHz. It is a subquantum-limited microwave
amplifier, it amplifies quantum noise above the added noise of commercial
amplifiers, and it squeezes quantum fluctuations by 10 dB.
