Amplitude and frequency sensing of microwave fields with a superconducting transmon qudit

Abstract

Experiments with superconducting circuits require careful calibration of the applied pulses and fields over a large frequency range. This remains an ongoing challenge as commercial semiconductor electronics are not able to probe signals arriving at the chip due to its cryogenic environment. Here, we demonstrate how the on-chip amplitude and frequency of a microwave signal can be inferred from the ac Stark shifts of higher transmon levels. In our time-resolved measurements we employ Ramsey fringes, allowing us to detect the amplitude of the systems transfer function over a range of several hundreds of MHz with an energy sensitivity on the order of 10 −4. Combined with similar measurements for the phase of the transfer function, our sensing method can facilitate pulse correction for high fidelity quantum gates in superconducting circuits. Additionally, the potential to characterize arbitrary microwave fields promotes applications in related areas of research, such as quantum optics or hybrid microwave systems including photonic, mechanical or magnonic subsystems.

Dissipation-Based Quantum Sensing of Magnons with a Superconducting Qubit

“…Counterintuitively, this results in the detection sensitivity being improved by increasing losses in the magnetostatic mode while operating close to or in the strong dispersive regime. The results presented here constitute an advancement in the detection and characterization of small magnon populations, and are also applicable to other physical systems in microwave quantum optics [6][7][8] and quantum acoustics [13][14][15], for example. The protocol demonstrated here therefore provides tools for a broad range of fields, from magnon spintronics to quantum sensing and hybrid quantum systems.…”

“…This property is leveraged in quantum sensing, where appropriate quantum systems can be monitored to detect a signal [1]. Superconducting qubits are attractive candidates for quantum sensors [1][2][3][4][5][6][7][8] as their large electric dipole moment enables strong coupling to electromagnetic fields [9,10]. Recent developments of hybrid quantum systems extend the range of applicability of qubits as quantum sensors through coupling the qubits to additional degrees of freedom [11][12][13][14][15][16].…”

Cryogenic power sensor enabling broad-band and traceable measurements

“…Although some detectors for itinerant microwave photons recently managed to reach single-photon sensitivity with efficiencies up to 96% [20][21][22] , they rely on discrete qubit transitions or on cavity-confined photons to facilitate detection 23,24 . This limits signal amplitude calibration to a narrow relative bandwidth 25 with the possibility of extending it to 1 GHz by observing a high-level ac Stark shift in a multilevel quantum system with a large frequency detuning 26,27 , but this extension comes at the cost of reduced energy sensitivity. Another method 28 enables absolute calibration of power over a gigahertz-wide frequency range by measuring the spectra of scattered radiation from a two-level system in a transmission line.…”

Engineering the microwave to infrared noise photon flux for superconducting quantum systems

“…They are at the core of technological transition to a so-called Noisy Intermediate-Scale Quantum (NISQ) level [ 2 ], where they are used for the construction of multi-qubit processors for quantum computation [ 3 ] and for the creation of structures to work as quantum simulators of other physical systems that are hard to study in a laboratory [ 4 , 5 ]. They also find applications in the sensing of amplitude, frequency [ 6 , 7 ] and power [ 8 ] of microwave signals and in quantum metrology [ 9 , 10 ]. For all of these tasks a quantum circuit needs to be well protected from external sources of decoherence, and precise control of the quantum state of the circuit and fast readout are required.…”