Multi-frequency spin manipulation using rapidly tunable superconducting coplanar waveguide microresonators

Abstract

In this work, we demonstrate the use of frequency-tunable superconducting NbTiN coplanar waveguide microresonators for multi-frequency pulsed electron spin resonance (ESR) experiments. By applying a bias current to the center pin, the resonance frequency (∼7.6 GHz) can be continuously tuned by as much as 95 MHz in 270 ns without a change in the quality factor of 3000 at 2K. We demonstrate the ESR performance of our resonators by measuring donor spin ensembles in silicon and show that adiabatic pulses can be used to overcome magnetic field inhomogeneities and microwave power limitations due to the applied bias current. We take advantage of the rapid tunability of these resonators to manipulate both phosphorus and arsenic spins in a single pulse sequence, demonstrating pulsed double electron-electron resonance (DEER). Our NbTiN resonator design is useful for multi-frequency pulsed ESR and should also have applications in experiments where spin ensembles are used as quantum memories.Superconducting microresonators have dramatically enhanced the detection sensitivity of conventional electron spin resonance (ESR). Recently, single-shot detection of 10 7 spins has been demonstrated at 2K using coplanar waveguide (CPW) resonators 1,2 , and further improvements in the readout at mK temperatures have enabled detection of 10 3 spins 3,4 using lumped-element resonators. As a result, these resonators are routinely used for the manipulation of spin ensembles and have also been proposed as buses for coherently coupling superconducting qubits with spins 5,6 . The resonance frequencies of CPW and lumped-element resonators are typically fixed by fabrication, and conventional methods used to tune the resonance frequency post-fabrication using superconducting quantum interference devices are incompatible with the high magnetic fields that are typically necessary for X-band ESR. A method that enables frequency tunability of superconducting microresonators at high magnetic fields is thus desirable for multifrequency ESR. The ability to tune the resonance frequency on-demand also allows greater control of spin dynamics 7,8 as well as the coupled spin-cavity dynamics in the strong-coupling regime where spin ensembles are used as quantum memories 6,9 . In this work, we fabricate frequency-tunable CPW resonators that are compatible with high magnetic fields following recently developed techniques 10-12 . We show multi-frequency ESR with 31 P donors in 28 Si, finding no effect on spin coherence when the resonators are operated at different frequencies. We show that the resonance frequency can be tuned in no more than ∼270 ns. As a practical application, we take advantage of the rapid tunability of our resonators to manipulate 31 P and 75 As donor spin ensembles that are 33 MHz apart in a single pulse sequence.

SKIFFS: Superconducting Kinetic Inductance Field-Frequency Sensors for sensitive magnetometry in moderate background magnetic fields

“…where f R0 = 4.182 GHz is the resonance frequency with B coil = 0 µT and B 0 = 60 mT. The functional form of the shift in the resonance frequency has been observed in other devices 1,9,[21][22][23] Three observations support this interpretation of the abrupt jumps in f R as B coil is swept. The first is the functional form in Eq.…”

“…The dynamic range can be extended by increasing the width of the nanowires. However, this choice comes at the expense of a loss in sensitivity, as wider nanowires reduce the kinetic inductance non-linearity of the loop 21 . In order to compensate for the reduced sensitivity, the loop area can be increased.…”

Storing quantum information in spins and high-sensitivity ESR

“…A final method to achieve fast control of resonator frequency makes use of photonic bandgap NbTiN resonators based on Bragg mirrors, where DC currents can be directly passed through the resonator to shift its frequency. This has been demonstrated using resonators with Q ∼ 3000, where a DC current of 3 mA resulted in a frequency shift of about 100 MHz, due to the impact of the bias current on the kinetic inductance [81].…”

Superefficient long-lived multiresonator quantum memory

“…Rather simple optimization scheme used by us at several spectral points does not require large computational resources and it can be also analyzed analytically on the basis of applied methods of algebraic geometry. [33][34][35][36] We note that the HMR scheme allows a very flexible spectral control (due to the dynamic control of parameters [37][38][39][40][41][42] ) for the transfer of quantum information from an external buffer to a long-lived electron spin ensembles through the system of high-quality miniresonators. That is, the proposed HMR QI provides an universal efficient scheme for storage of broadband light fields.…”