Experimental demonstration of two-photon magnetic resonances in a single-spin system of a solid

While the manipulation of quantum systems has been significantly developed, achieving a single-source multiuse system for quantum-information processing and networks is still challenging. A virtual state, a so-called dressed state, is a potential host for quantum hybridizations of quantum physical systems with various operational ranges. We present an experimental demonstration of a dressed state generated by two-photon magnetic resonances using a single spin in a single nitrogen-vacancy center in diamond. The two-photon magnetic resonances occur under the application of microwave and radio-frequency fields, with different operational ranges. The experimental results reveal the behavior of two-photon magnetic transitions in a single defect spin in a solid, thus presenting potential quantum and semiclassical hybrid systems with different operational ranges using superconductivity and spintronics devices.

Figure 1

(a) Diagram of our experiment using two-photon magnetic resonance. (b) Energy diagram of an NV center under a static magnetic field ($B_0$) along the NV axis.

Figure 2

(a) Homemade confocal microscope with a system for electromagnetic-field irradiation. A 532-nm laser excites an NV center. Photoluminescence is detected by two avalanche photodiodes (APD). Pump and probe fields are combined by a frequency diplexer and are irradiated on the sample via a thin copper wire. (b) Photoluminescence scanning image of NV centers in diamond. The red circle shows the single NV center used in this experiment. (c) $g^{\left(2\right)}\left(\tau \right)$ of the fluorescence light emitted by the NV center. (d) Pulse sequence to generate a TPMR by means of a pump field. The pump field is irradiated continuously during both laser illumination and probe field irradiation.

Figure 3

(a) ODMR spectra by sweeping the frequency of a 5.5-$\mu \mathrm{s}$ probe field with and without irradiation by a continuous pump field, revealing the ${}^{14}\mathrm{N}$ nuclear hyperfine structure. The black, red, orange, pink, and blue plots show spectra for pump fields of 63.0, 31.6, 10.0, 2.00, and 0.63 mW, respectively. The brown plot shows the ODMR spectrum without a pump field. The solid lines show the fitting for each ODMR spectrum. The scale bar indicates a $\mathrm{\Delta }PL/PL$ of 0.005. (b) Energy levels of a TPMR under the application of a pump field with a frequency of 5.3 MHz.

Figure 4

(a) ODMR spectrum with a 5.3-MHz pump field, as shown in Fig. 3. The solid red line shows a fit using the sum of nine Gaussian peaks. (b) Peak position shifts due to changes in the pump field frequency. (c) ODMR spectrum without a pump field. The probe field has a length of 5.5 $\mu \mathrm{s}$ and is sufficiently weak to allow the ${}^{14}\mathrm{N}$ nuclear hyperfine structure to be observed. The solid red line shows a fit using the sum of three Gaussian peaks.

Figure 5

Characterization of the output frequencies of the pump field with a diplexer as functions of (a) the pump power with a fixed pump frequency of 5.3 MHz and (b) the pump frequency with a fixed pump power of 63 mW, with a probe frequency of 2822 MHz and probe power at 10 $\mu \mathrm{W}$.

Figure 6

(a) Two-level system of $E_{\alpha }$ and $E_{\beta }$. (b) Configuration of a static magnetic field ($B_0$), mw field (${\omega }_1$), and rf field (${\omega }_2$) in the laboratory frame. (c) Configuration of the singly rotating frame. (d) Configuration of the doubly rotating frame.

Figure 7

Intensity of the TPMR as a function of rf frequency. The data points show the experimental results and the solid line shows the simulation result (details in main text).