Valdis Blums

Controllable optical phase shift over one radian from a single isolated atom.

Fundamental optics such as lenses and prisms work by applying phase shifts of several radians to incoming light, and rapid control of such phase shifts is crucial to telecommunications. However, large, controllable optical phase shifts have remained elusive for isolated quantum systems. We have used a single trapped atomic ion to induce and measure a large optical phase shift of 1.3±0.1 radians in light scattered by the atom. Spatial interferometry between the scattered light and unscattered illumination light enables us to isolate the phase shift in the scattered component. The phase shift achieves the maximum value allowed by atomic theory over the accessible range of laser frequencies, pointing out new opportunities in microscopy and nanophotonics. Single-atom phase shifts of this magnitude open up new quantum information protocols, in particular long-range quantum phase-shift-keying cryptography.

Single atom sub atto-newton force sensor in three-dimensions

Ultra-sensitive force measurements are crucial for physics. Nanometer precision displacement measurements of a Paul trapped ¹⁷⁴Yb⁺ ion provides force sensitivities below aN/√Hz. Accuracy was verified by measuring the 95 zN cooling laser light force pressure.

Integrated Fresnel Mirrors for scalable trapped ion quantum computing

Photonic interconnects are a bottleneck to achieving large-scale trapped ion quantum computing. We fabricated a surface trap with diffractive mirrors and achieved sub-wavelength imaging of a trapped ion and 2.0±0.5% coupling into a single-mode fiber.

Scalable trapped-ion single-photon sources with monolithically integrated optics

We demonstrate the first fully integrated and scalable diffractive mirrors for efficient ion light collection. We also generated single photons using an Yb+ ion and collected them using these mirrors to do a quantum communication protocol.

Monolithic optical integration for scalable trapped-ion quantum information processing

Quantum information processing (QIP) promises to radically change the outlook for secure communications, both by breaking existing cryptographic protocols and offering new quantum protocols in their place. A promising technology for QIP uses arrays of atomic ions that are trapped in ultrahigh vacuum and manipulated by lasers. Over the last several years, work in my research group has led to the demonstration of a monolithically integrated, scalable optical interconnect for trapped-ion QIP. Our interconnect collects single photons from trapped ions using a diffractive mirror array, which is fabricated directly on a chip-type ion trap using a CMOS-compatible process. Based on this interconnect, we have proposed an architecture that couples trapped ion arrays with photonic integrated circuits to achieve compatibility with current telecom networks. Such tightly integrated, highly parallel systems open the prospect of long-distance quantum cryptography.

Large optical phase shift from a single trapped atomic ion

In this paper, we have observed a large optical phase shift of 1.3±01 radian from a single ion. The phase shift can be controlled by changing the detuning of the illumination laser. This scheme might find application in quantum computing and quantum information processing.

Imaging a single atom's absorption and phase shift

We have used a single trapped atomic ion to induce and measure a large optical phase shift of 1.3 radians in light scattered by the atom by utilizing spatial interferometry based on absorption imaging.