Observation of atomic localization using electromagnetically induced transparency

Abstract

We present a proof-of-principle experiment in which the population of an atomic level is spatially localized using the technique of electromagnetically-induced transparency (EIT). The key idea is to utilize the sensitive dependence of the dark state of EIT on the intensity of the coupling laser beam. By using a sinusoidal intensity variation (standing-wave), we demonstrate that the population of a specific hyperfine level can be localized much tighter than the spatial period.It is well-known that traditional optical techniques cannot resolve or write features smaller than half the wavelength of light. This barrier, known as the diffraction limit, has important implications for a variety of scientific research areas including biological microscopy and quantum computation. As an example, in a neutralatom quantum computing architecture, the diffraction limit prohibits high-fidelity manipulation of individual atoms if they are separated by less than the wavelength of light. Recently, Agarwal and others [1][2][3] have proposed to use the dark state of electromagnetically induced transparency (EIT) [4,5] to address atoms at potentially nanometer spatial scales. This technique relies on the sensitive dependence of the dark state to the intensities of the driving probe and coupling laser beams. If a standing-wave coupling laser is used, the population of the excited Raman level can be very tightly localized near the intensity nodes, allowing for sub-wavelength control. In this letter, we present a proof-of-principle experiment that demonstrates the key ideas of this approach. By using ultracold Rubidium (Rb) atoms in a magneto-optical trap (MOT) and pulsed coherent transfer, we demonstrate atomic localization to spots much smaller than the spatial period of the coupling-laser intensity profile. Although due to imaging limitations we have used a large spatial period in this work (≈ 600 µm), our results will likely scale to the sub-wavelength regime in the future.Before proceeding, we cite important prior work leading up to this experiment. In their pioneering work, Thomas and colleagues have suggested and experimentally demonstrated sub-wavelength position localization of atoms using spatially varying energy shifts [6][7][8]. Zubairy and coworkers have discussed atom localization using resonance fluorescence and phase and amplitude control of the absorption spectrum [9][10][11]. Knight and colleagues discussed localization via quantum interference at the probability amplitude of the excited electronic state [12]. Li et. al. have experimentally demonstrated probe narrowing beyond the diffraction limit using a spatially-varying coupling laser profile in a vapor cell [13]. There has also been remarkable progress in utilizing the position dependent stimulated emission to achieve nanoscale resolution [14,15]. This last approach, also known as stimulated-emission depletion microscopy, is now a widely used technique in biological imaging. We note that our approach of using the dark state for atomic localization has the followin...

Refractive Index Enhancement in Gases

“…(iii) We have experimentally demonstrated a new type of coherent atomic localization with ultracold atoms using the dark state of EIT [5]. With future improvements, dark-state based localization may evolve into a powerful technique for addressing and manipulating atoms at subwavelength spatial scales with significant implications for quantum computing.…”

“…A detailed description of this experiment can be found in Ref. [5]. Briefly, we set up an EIT Λ scheme in 87 Rb using |F = 1 → |F = 2 and |F = 2 → |F = 2 transitions with the probe and coupling laser beams respectively.…”

Precision localization of single atom via spontaneous emission in three dimensions

“…Also, one-dimensional (1D) atom localization can be realized via dual measurement of the field and the atomic internal state [18], double-dark resonance effects [19], phase and amplitude control of the driving field [20,21], coherent manipulation of the Raman gain process [22], or spontaneous emission [23,24]. Recently, atom localization has been demonstrated in a proof-of-principle experiment using the technique of electromagnetically induced transparency (EIT) [25]. Apart from the above-mentioned 1D atom localization, some schemes have been put forward for two-dimensional (2D) atom localization by applying two orthogonal standing-wave laser fields.…”

Influence of interaction time and population redistribution on the localization of atomic excitation through electromagnetically induced transparency

“…It is of great interest [1][2][3][4][5][6][7][8][9][10][11][12][13] to devise techniques for reducing this limit, however, so that one might be able to locally control the interaction of the field with two or more atoms that are separated in space by a distance much less than this diffraction limit. Early work [3][4][5] on subwavelength localization, as this effect is called, was based upon spatially varying perturbations, such as a Zeeman shift caused by an inhomogeneous magnetic field or the ac Stark shift caused by the intensity gradient of the spatial profile of a focused laser beam.…”

“…Early work [3][4][5] on subwavelength localization, as this effect is called, was based upon spatially varying perturbations, such as a Zeeman shift caused by an inhomogeneous magnetic field or the ac Stark shift caused by the intensity gradient of the spatial profile of a focused laser beam. More recently, advances in localization through electromagnetically induced transparency (EIT) have been reported [6][7][8][9][10][11][12][13]. In these schemes, an atomic three-level -type system is excited by a pair of coherent laser fields, one resonant with each of the two electric-dipole allowed transitions in the system.…”