Andrew Schwarzkopf

Sub-wavelength imaging and field mapping via electromagnetically induced transparency and Autler-Townes splitting in Rydberg atoms

We present a technique for measuring radio-frequency (RF) electric field strengths with sub-wavelength resolution. We use Rydberg states of rubidium atoms to probe the RF field. The RF field causes an energy splitting of the Rydberg states via the Autler-Townes effect, and we detect the splitting via electromagnetically induced transparency (EIT). We use this technique to measure the electric field distribution inside a glass cylinder with applied RF fields at 17.04 GHz and 104.77 GHz. We achieve a spatial resolution of ≈100 μm, limited by the widths of the laser beams utilized for the EIT spectroscopy. We numerically simulate the fields in the glass cylinder and find good agreement with the measured fields. Our results suggest that this technique could be applied to image fields on a small spatial scale over a large range of frequencies, up into the sub-terahertz regime.

Millimeter wave detection via Autler-Townes splitting in rubidium Rydberg atoms

In this paper, we demonstrate the detection of millimeter waves via Autler-Townes splitting in 85Rb Rydberg atoms. This method may provide an independent, atom-based, SI-traceable method for measuring mm-wave electric fields, which addresses a gap in current calibration techniques in the mm-wave regime. The electric-field amplitude within a rubidium vapor cell in the WR-10 wave guide band is measured for frequencies of 93.71 GHz and 104.77 GHz. Relevant aspects of Autler-Townes splitting originating from a four-level electromagnetically induced transparency scheme are discussed. We measured the E-field generated by an open-ended waveguide using this technique. Experimental results are compared to a full-wave finite element simulation.

Broadband Rydberg Atom-Based Electric-Field Probe for SI-Traceable, Self-Calibrated Measurements

We discuss a fundamentally new approach for the measurement of electric (E) fields that will lead to the development of a broadband, direct SI-traceable, compact, se lfcalibrating E-field probe (sensor). This approach is based o n the interaction of radio frequency (RF) fields with alkali atoms excited to Rydberg states. The RF field causes an energy split ting of the Rydberg states via the Autler-Townes effect and we det ct the splitting via electromagnetically induced transparency (EIT). In effect, alkali atoms placed in a vapor cell act like an RFto-optical transducer, converting an RF E-field strength measurement to an optical frequency measurement. We demonstra te the broadband nature of this approach by showing that one small vapor cell can be used to measure E-field strengths over a wide range of frequencies: 1 GHz to 500 GHz. The technique is validated by comparing experimental data to both numerical simulations and far-field calculations for various frequencies. We also discuss various applications, including: a direct traceable measurement, the ability to measure both weak and strong fiel d strengths, compact form factors of the probe, and sub-wavelngth imaging and field mapping.We discuss a fundamentally new approach for the measurement of electric (E) fields that will lead to the development of a broadband, direct SI-traceable, compact, self-calibrating E-field probe (sensor). This approach is based on the interaction of radio frequency (RF) fields with alkali atoms excited to Rydberg states. The RF field causes an energy splitting of the Rydberg states via the Autler-Townes effect and we detect the splitting via electromagnetically induced transparency. In effect, alkali atoms placed in a vapor cell act like an RF-to-optical transducer, converting an RF E-field strength measurement to an optical frequency measurement. We demonstrate the broadband nature of this approach by showing that one small vapor cell can be used to measure E-field strengths over a wide range of frequencies: 1 GHz to 500 GHz. The technique is validated by comparing experimental data to both numerical simulations and far-field calculations for various frequencies. We also discuss various applications, including: a direct traceable measurement, the ability to measure both weak and strong field strengths, compact form factors of the probe, and sub-wavelength imaging and field mapping.

Measurement of the van der Waals interaction by atom trajectory imaging

a single-atom imaging technique. From the average pair correlation function of the atom positions we obtain the initial atom-pair separation and the terminal velocity, which yield the van der Waals interaction coecient C6. The measured C6 value agrees well with calculations. The experimental method has been validated by simulations. The data hint at anisotropy in the overall expansion, caused by the shape of the excitation volume. Our measurement implies that the interacting entities are individual Rydberg atoms, not groups of atoms that coherently share a Rydberg excitation. PACS numbers: 32.80.Ee, 34.20.Cf

Atom-based RF electric field measurements: An initial investigation of the measurement uncertainties

We discuss a new method for the measurement of electric (E) fields that will lead to a self-calibrating, direct SI-traceable E-field probe. The technique is based on radio frequency E-field interactions with alkali atoms placed in glass cells. After we present the concept of this approach and present some experimental data to show its validity, we give a discussion of the different types of uncertainties that are associated with this new approach. We discuss how the uncertainties of this approach compare to commonly used E-field measurement techniques.

Control of Spatial Correlations between Rydberg Excitations using Rotary Echo

We manipulate correlations between Rydberg excitations in cold atom samples using a rotary-echo technique in which the phase of the excitation pulse is flipped at a selected time during the pulse. The correlations are due to interactions between the Rydberg atoms. We measure the resulting change in the spatial pair correlation function of the excitations via direct position-sensitive atom imaging. For zero detuning of the lasers from the interaction-free Rydberg-excitation resonance, the pair-correlation value at the most likely nearest-neighbor Rydberg-atom distance is substantially enhanced when the phase is flipped at the middle of the excitation pulse. In this case, the rotary echo eliminates most uncorrelated (unpaired) atoms, leaving an abundance of correlated atom pairs at the end of the sequence. In off-resonant cases, a complementary behavior is observed. We further characterize the effect of the rotary-echo excitation sequence on the excitation-number statistics.

Atom-based RF field probe: From self-calibrated measurements to sub-wavelength imaging

In this presentation, we discuss a fundamentally new approach for an electric (E) field probe design. This new approach is significantly different than currently used field probes in that it is based on the interaction of RF-fields with Rydberg atoms (alkali atoms placed in a glass vapor cell are excited optically to Rydberg states). The applied RF-field alters the resonant state of the atoms. The Rydberg atoms act like an RF-to-optical transducer, converting an RF E-field to an optical-frequency response. The RF probe utilizes the concept of Electromagnetically Induced Transparency (EIT). The RF transition in the four-level atomic system causes a split of the EIT transmission spectrum for a probe laser. This splitting is easily measured and is directly proportional to the applied RF field amplitude. The significant dipole response of Rydberg atoms enables this technique to make self-calibrating measurements over a large frequency band including 1-500 GHz. In this paper, we report on our results in the development of this probe. We also discuss two key applications: that is, self-calibrated measurements and sub-wavelength imaging and field mapping.

Broadband Rydberg atom based self-calibrating RF E-field probe

We present a significantly new approach for an electric (E) field probe design. The probe is based on the interaction of RF-fields with Rydberg atoms, where alkali atoms are excited optically to Rydberg states and the applied RF-field alters the resonant state of the atoms. For this probe, the Rydberg atoms are excited in a glass vapor cell. The Rydberg atoms act like an RF-to-optical transducer, converting an RF E-field to an optical-frequency response. The probe utilizes the concept of Electromagnetically Induced Transparency (EIT). The RF transition in the four-level atomic system causes a split of the EIT transmission spectrum for the probe laser. This splitting is easily measured and is directly proportional to the applied RF field amplitude. Therefore, by measuring this splitting we get a direct measurement of the RF E-field strength. The significant dipole response of Rydberg atoms over the GHz regime enables this technique to make traceable measurements over a large frequency band including 1-500 GHz. We will show that, with one probe, measurements can be made over a very large frequency range. This is a truly broadband probe/sensor. In this paper, we report on our results in the development of this probe.