Quantum Mixer to Sense Arbitrary-Frequency Fields

Quantum sensors, such as nitrogen-vacancy (NV) centers in diamond, have revolutionized the field of precision measurement by offering exceptional sensitivity and spatial resolution. These sensors are pivotal in applications ranging from magnetic-field detection to nanoscale imaging, in which high accuracy and detailed spatial information are crucial. The growing demand for versatile sensing technologies across various scientific and industrial domains underscores the need for sensors that can operate effectively over a wide range of frequencies. As technologies advance, the ability to detect and analyze signals at arbitrary frequencies becomes increasingly important for applications in telecommunications, biomedical imaging, and fundamental physics research. However, current quantum sensor technologies face significant limitations in their operational frequency ranges. Typically, these sensors are confined to detecting signal fields within specific, narrow frequency bands, constrained by the experimentally achievable control field amplitudes and their inherent resonance frequencies. This restriction hampers their utility in scenarios requiring the detection of intermediate (50 MHz to 2 GHz) and ultrahigh frequency signals (above a few GHz). Additionally, existing sensing protocols often struggle with issues such as limited bandwidth, low signal-to-noise ratios, and the inability to distinguish vectorial components of oscillating fields. These challenges prevent quantum sensors from fully realizing their potential in diverse applications, highlighting the urgent need for innovative approaches to overcome the frequency detection barriers and enhance the versatility of quantum sensing technologies.

Technology Description

Quantum sensors achieve high sensitivity and spatial resolution but are typically limited to detecting signal fields within specific frequency ranges. This technology utilizes the sensor qubit as a frequency mixer, enabling the detection of arbitrary-frequency signals by leveraging nonlinear effects in periodically driven (Floquet) quantum systems. By combining the signal with an applied AC bias field, a frequency-mixed field is generated, which can be detected using established sensing techniques such as Rabi oscillations and CPMG sequences. The system comprises components like nitrogen-vacancy centers in diamond, an AC bias field generator, signal detection antenna, state measurement detector, and signal processing unit. This approach facilitates vector magnetometry across a broad frequency spectrum, as demonstrated by the ability to sense a 150 MHz signal field using NV centers.

What sets this technology apart is its ability to significantly expand the operational frequency range of quantum sensors beyond traditional limitations. Unlike conventional quantum sensors that are confined to narrow frequency windows near their resonance frequencies, the quantum frequency mixing technique allows for the detection of signals across intermediate (50 MHz to 2 GHz) and ultrahigh frequency ranges (above a few GHz). The integration of Floquet theory and nonlinear mixing effectively translates off-resonant signals into detectable frequencies, enhancing versatility and applicability. Additionally, the capability for vector field sensing enables simultaneous measurement of both amplitude and direction of AC fields at arbitrary frequencies. This innovation maintains high sensitivity and nanoscale resolution while overcoming the constraints of existing quantum sensing technologies, opening new possibilities for precise electromagnetic signal detection across a wide frequency spectrum.