Ultrasensitive, Parity-Time-Symmetric Wireless Reactive and Resistive Sensors

We propose a new readout paradigm for enhancing the performance of wireless resistive and reactive sensors. Here, we consider a passive resistor-inductor-capacitor sensor that is inductively coupled to an active reader, with the equivalent circuit of the whole telemetry system obeying the space-time reflection symmetry or the parity-time (PT) symmetry. As inspired by PT-symmetric quantum systems, this circuit has a non-Hermitian effective Hamiltonian that commutes with the antilinear, combined PT operator, where P and T are parity-inversion and time-reversal operators. We demonstrate that the PT-symmetric wireless sensor system, when compared to conventional interrogation techniques using a passive coil antenna, may provide significantly improved quality factor (Q-factor), sensing resolution, and sensitivity in response to the sensor's reactance or resistance variation. Our results may have an impact on various wireless sensing, detection, and imaging systems, particularly for emerging micromachined sensors, miniature implants, wearables, and Internet-of-Things applications.