Time Crystals as quantum sensors of AC fields

The long-range spatial and temporal ordering displayed by discrete time crystals, can become advantageous properties when used for sensing extremely weak signals. I will discuss their performance as quantum sensors of weak ac fields and show that they can overcome the shot-noise limit while allowing long interrogation times. In such systems, collective interactions stabilize their dynamics against noise, making them robust enough to protocol imperfections. Furthermore, I will also consider dissipative time crystals showing that also in this case enhanced sensitivity is present when spins are resonant with the applied AC field.