Total Control of Ultracold Atoms Control of Ultracold Atoms Has the Potential to Improve Tremendously Our Understanding of Strongly Correlated Quantum Systems

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IMAGING AND MANIPULATION Total control of ultracold atoms 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 © 2013 AIP atoms, while also enabling high-resolution in-trap optical imaging (Appl. Phys. Lett. the ultracold atoms are in vacuum, they replaced by on-chip components 102, 084104; 2013). are also very close to the outside world,” such as refractive, diffractive and The device has a compound explained Anderson. This enables very holographic elements. The researchers substrate consisting of coplanar high-resolution access to the ultracold have therefore established the viability regions of glass and silicon, measures atoms in a high-vacuum system using of integrated magnetic and optical 23 mm × 23 mm × 420 μm with a 3 mm optics that reside outside the miniature ultracold atom systems of interest for polished glass region in the centre vacuum cell, thus allowing commercial future applications. of the substrate, and supports 60 microscope objectives to be used. “Our interest is the development ultrahigh-vacuum-compatible electrical The researchers also used of atomtronic devices, such as atom feedthroughs. Conventional lithographic holographically generated light patterns transistors and diodes, and circuits, such patterning and metallization enable to optically slice a cigar-shaped magnetic as atom amplifiers, de Broglie filters and magnetic trapping and glass regions trap into separate regions, generating up matter-wave oscillators. Our long-term permit high-numerical-aperture optical to four Bose–Einstein condensates. They objective is to develop quantum signal access to atoms in the magnetic trap, demonstrated in-trap imaging down to a processing systems that are analogous which is about 100 μm below the resolution of 2.5 μm. to classical ones implemented with chip surface. The atom chip is particularly interesting electronics. Such systems have potential “The core portion of the apparatus — for its use in time keeping, sensing, applications in sensing, for example in the vacuum system — is simple and studying condensed-matter systems conjunction with atom interferometry compact. A key feature is that the atom and performing quantum simulations and quantum information processing,” chip also serves as a wall of the vacuum and quantum information processing. said Anderson. system rather than residing inside the According to Anderson, their optical vacuum system. This means that although projection set-up could eventually be RACHEL WON

QUANTUM CRYPTOGRAPHY Continuous improvement Using photons to disseminate encryption codes with complete security is one of the great successes of quantum information science. It has now been shown that long-distance cryptographic communication is just as effective when the scheme involves measuring the wave properties of light, rather than its particle properties. P. K. Lam and T. C. Ralph

he popularity of quantum quantum cryptography is arguably the first In the first, the individual properties — cryptography originates largely from technology that relies on a quantitative referred to as discrete variables (DVs) — of Tits tantalizing promise of providing understanding of quantum correlations, single photons (such as their polarization) communication that is absolutely secure known as entanglement. Several companies are used as non-orthogonal bases for against eavesdropping. Unlike conventional are already selling turnkey QKD systems, measurements. This was the case in the cryptography, the security of quantum and national agencies are establishing original QKD protocol called BB84, which key distribution (QKD) is founded on the national standards for their usage. was first reported in 19841, as well as in laws of physics rather than mathematical QKD is generally implemented in one many subsequent QKD protocols. In complexity1. Although still nascent, of two experimental approaches (Fig. 1). contrast, the second approach uses the field