Quantum Experiments

Our single-atom sensitive optical microscope provides us with a tool to directly investigate quantum processes. Using laser cooled atoms, we exploit the fundamental wave-nature of matter to build an interferometer that uses atoms as the interfering waves. We put each atom into a coherent superposition of different momentum states which then simultaneously traverse the different paths in the interferometer. The sinsitivity of atomic interferometers plays an essential role in many high precision measurements. Watching how small groups of atoms behave when exposed to externally controlled laser pulses gives us new knowledge about the quantum world, that we use to understand complex systems, and for the development of future technologies such as quantum computers.


Our experiments use an ultracold atom machine that produces atomic gas samples at nanokelvin temperatures - temperatures where the wave nature of particles becomes dominant, and particles separate into two classes that behave socially (Bosons) or anti-socially (Fermions), due to their quantum statistics.


Our machine can produce Bose-Einstein condensates of Rb-87 atoms as well as quantum degenerate Fermi gases of K-40 atoms.  Using laser beams to accelerate clouds of ultra-cold atoms, we can observe collisions between degenerate quantum systems with exquisite resolution.


Quantum Optics techniques allow quantum states of light and atoms to be controlled and studied using lasers and high quality optical resonators. Quantum states can also be efficiently transferred between atoms and light, setting the scene for quantum information processing, involving storage, retrieval, transmission and computation. Rare-earth atoms such as Lanthanum are essential for consumer electronics, but they also have excellent properties for quantum information processing. We specialise in the application of rare-earth-ion doped solids to quantum information, quantum computing and signal processing optics. Currently our areas of research focus are whispering gallery mode resonators, the optical detection of ultrasound, quantum memories and the generation of entangled light.


By utilizing continued total internal reflection, whispering gallery mode resonators can confine light tightly and provide access to strong non-linear interactions even at low input powers. 


Our research focuses on using such resonators to achieve efficient non-linear interactions between far removed frequency ranges, mixing microwave radiation with optical light to generate light of different colour. Such conversion can in principle be perfect and therefore be used in schemes where quantum information of light in the microwave domain can be transferred into the optical domain - opening a route towards future quantum networks. Such high quality resonators can also be used in classical optics where they are used as sensors to detect the smallest changes in the environment.


The Centre for Quantum Science is  a University of Otago Research Centre hosted by the Department of Physics.


Department of Physics

University of Otago

730 Cumberland Street

Dunedin 9010



Ashton Bradley                       

ashton.bradley [at] otago.ac.nz    


Niels Kjærgaard            

niels.kjaergaard [at] otago.ac.nz