Recent advances in device fabrication techniques and quantum control methodology have enabled the demonstration of novel spin-cavity physics and high-sensitivity electron paramagnetic resonance (EPR) measurements on spin ensembles coupled to superconducting resonators. For certain specialized setups, the benefits of superconducting resonators can be substantial, but long pulse lengths, low-device bandwidth, and small sample sizes (∼nL) limit the scope of applications. To perform more general EPR measurements, including protein distance measurements in biophysical EPR, superconducting resonators must be capable of transmitting higher power (>1 Watt) and higher bandwidth (>100 MHz) pulses to larger samples (∼μL). We present a new class of superconducting resonators, based on a multi-microstrip design, that enable high sensitivity EPR measurements on 2.4 μL samples with Rabi fields up to 20 G for 10 Watts pulse power, control and detection bandwidths greater than 100 MHz, and field uniformity sufficient to perform complex multiple pulse experiments. We will focus on the design principles of the devices, including adaptable broadband coupling methods and spatial microwave field profile engineering. A variety of validation experiments demonstrate the performance of the device, including nutation measurements, CPMG measurements, and distance measurements on low concentration (<10 μM) spin-labelled protein samples using AWG shaped pulses.
Troy W. Borneman (Sun,) studied this question.