Ghost imaging is a counter-intuitive phenomenon—first realized in quantum optics1, 2—that enables the image of a two-dimensional object (mask) to be reconstructed using the spatio-temporal properties of a beam of particles with which it never interacts. Typically, two beams of correlated photons are used: one passes through the mask to a single-pixel (bucket) detector while the spatial profile of the other is measured by a high-resolution (multi-pixel) detector. The second beam never interacts with the mask. Neither detector can reconstruct the mask independently, but temporal cross-correlation between the two beams can be used to recover a ‘ghost’ image. Here we report the realization of ghost imaging using massive particles instead of photons. In our experiment, the two beams are formed by correlated pairs of ultracold, metastable helium atoms3, which originate from s-wave scattering of two colliding Bose–Einstein condensates4, 5. We use higher-order Kapitza–Dirac scattering6, 7, 8 to generate a large number of correlated atom pairs, enabling the creation of a clear ghost image with submillimetre resolution. Future extensions of our technique could lead to the realization of ghost interference9, and enable tests of Einstein–Podolsky–Rosen entanglement9 and Bell’s inequalities10 with atoms.
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Extended data figures and tables
Extended Data Figures
- Extended Data Figure 2: Ghost image visibility. (215 KB)
Visibilities (dots) for images (insets) reconstructed from each individual halo with different average numbers of atoms . Diffraction orders producing the halos are labelled as ( + 1, ). The dashed curve is a guide to the eye. Error bars represent the standard error of the mean associated with the variances of the pixel values contributing to I and B.