Control of ultracold atoms has the potential to improve tremendously our understanding of strongly correlated quantum systems. Now, Dana Anderson and co-workers at the University of Colorado at Boulder and the National Institute of Standards and Technology in the USA have demonstrated a hybrid atom chip system that allows the simultaneous high-spatial-resolution magnetic and optical control of ultracold atoms, while also enabling high-resolution in-trap optical imaging (Appl. Phys. Lett. 102, 084104; 2013).

The device has a compound substrate consisting of coplanar regions of glass and silicon, measures 23 mm × 23 mm × 420 μm with a 3 mm polished glass region in the centre of the substrate, and supports 60 ultrahigh-vacuum-compatible electrical feedthroughs. Conventional lithographic patterning and metallization enable magnetic trapping and glass regions permit high-numerical-aperture optical access to atoms in the magnetic trap, which is about 100 μm below the chip surface.

Credit: © 2013 AIP

“The core portion of the apparatus — the vacuum system — is simple and compact. A key feature is that the atom chip also serves as a wall of the vacuum system rather than residing inside the vacuum system. This means that although the ultracold atoms are in vacuum, they are also very close to the outside world,” explained Anderson. This enables very high-resolution access to the ultracold atoms in a high-vacuum system using optics that reside outside the miniature vacuum cell, thus allowing commercial microscope objectives to be used.

The researchers also used holographically generated light patterns to optically slice a cigar-shaped magnetic trap into separate regions, generating up to four Bose–Einstein condensates. They demonstrated in-trap imaging down to a resolution of 2.5 μm.

The atom chip is particularly interesting for its use in time keeping, sensing, studying condensed-matter systems and performing quantum simulations and quantum information processing. According to Anderson, their optical projection set-up could eventually be replaced by on-chip components such as refractive, diffractive and holographic elements. The researchers have therefore established the viability of integrated magnetic and optical ultracold atom systems of interest for future applications.

“Our interest is the development of atomtronic devices, such as atom transistors and diodes, and circuits, such as atom amplifiers, de Broglie filters and matter-wave oscillators. Our long-term objective is to develop quantum signal processing systems that are analogous to classical ones implemented with electronics. Such systems have potential applications in sensing, for example in conjunction with atom interferometry and quantum information processing,” said Anderson.