  Fast and high-fidelity qubit measurement is essential for realizing quantum
error correction, which is in turn a key ingredient to universal quantum
computing. For electron spin qubits, fast readout is one of the significant
road blocks toward error correction. Here we examine the dispersive readout of
a single spin in a semiconductor double quantum dot coupled to a microwave
resonator. We show that using displaced squeezed vacuum states for the probing
photons can improve the qubit readout fidelity and speed. Under condition of
proper phase matching, we find that a moderate, and only moderate, squeezing
can enhance both the signal-to-noise ratio and the fidelity of the qubit-state
readout, and the optimal readout time can be shortened to the sub-microsecond
range with above $99\%$ fidelity. These enhancements are achieved at low
probing microwave intensity, ensuring non-demolition qubit measurement.
