  Recently, we introduced a Rydberg-atom based mixer capable of detecting and
measuring the phase of a radio-frequency field through the electromagnetically
induced transparency (EIT) and Autler-Townes (AT) effect. The ability to
measure phase with this mixer allows for an atom-based receiver to detect
digital modulated communication signals. In this paper, we demonstrate
detection and reception of digital modulated signals based on various
phase-shift keying approaches. We demonstrate Rydberg atom-based digital
reception of binary phase-shift keying (BPSK), quadrature phase-shift keying
(QPSK), and quadrature amplitude (QAM) modulated signals over a 19.626~GHz
carrier to transmit and receive a bit stream in cesium vapor. We present
measured values of Error Vector Magnitude (EVM, a common communication metric
used to assess how accurate a symbol or bit stream is received) as a function
of symbol rate for BPSK, QPSK, 16QAM, 32QAM, and 64QAM modulation schemes.
These results allow us to discuss the bandwidth of a Rydberg-atom based
receiver system.
