Dynamic decoherence control of a solid-state nuclear-quadrupole qubit

We report on the application of a dynamic decoherence control pulse sequence on a nuclear-quadrupole transition in Pr3+∶Y2SiO5. Process tomography is used to analyze the effect of the pulse sequence. The pulse sequence was found to increase the decoherence time of the transition to over 30 seconds. Although the decoherence time was significantly increased, the population terms were found to rapidly decay on the application of the pulse sequence. The increase of this decay rate is attributed to inhomogeneity in the ensemble. Methods to circumvent this limit are discussed

Analytic treatment of controlled reversible inhomogeneous broadening quantum memories for light using two-level atoms

It has recently been discovered that the optical analog of a gradient echo, in an optically thick material, could form the basis of an optical memory that is both completely efficient and noise-free. Here we present analytical calculations showing that this is the case. There is close analogy between the operation of the memory and an optical system with two beam splitters. We can use this analogy to calculate efficiencies as a function of optical depth for a number of quantum memory schemes based on controlled inhomogeneous broadening. In particular, we show that multiple switching leads to a net 100% retrieval efficiency for the optical gradient echo even in the optically thin case

Solid state coherent transient measurements using hard optical pulses

An isolated and spectrally narrow absorptive feature is prepared via a novel spectral hole burning process in an inhomogeneously broadened optical transition in Eu3+:Y2SiO5. With the narrow feature it is shown that it is feasible to apply complex optical pulse sequences analogous to rf pulse sequences used extensively in NMR

Photon echo without a free induction decay in a double-Lambda system

We have characterized a novel photon-echo pulse sequence for a double-$\Lambda$ type energy level system where the input and rephasing transitions are different to the applied $\pi$-pulses. We show that despite having imperfect $\pi$-pulses (associated with large coherent emission due to free induction decay), the noise added is only 0.019$\pm$0.001 relative to the shot noise in the spectral mode of the echo. Using this echo pulse sequence in the `rephased amplified spontaneous emission' (RASE) scheme \cite{Ledingham2010} will allow for generation of entangled photon pairs that are in different frequency, temporal, and potentially spatial modes to any bright driving fields. The coherence and efficiency properties of this sequence were characterized in a Pr:YSO crystal

The observation of photon echoes from evanescently coupled rare-earth ions in a planar waveguide

We report the measurement of the inhomogeneous linewidth, homogeneous linewidth and spin state lifetime of Pr3+ ions in a novel waveguide architecture. The TeO2 slab waveguide deposited on a bulk Pr3+:Y2SiO5 crystal allows the 3H4 - 1D2 transition of Pr3+ ions to be probed by the optical evanescent field that extends into the substrate. The 2 GHz inhomogeneous linewidth, the optical coherence time of 70 +- 5 us, and the spin state lifetime of 9.8 +- 0.3 s indicate that the properties of ions interacting with the waveguide mode are consistent with those of bulk ions. This result establishes the foundation for large, integrated and high performance rare-earth-ion quantum systems based on a waveguide platform.Comment: 5 pages, 5 figure

Quantum information processing using frozen core Y 3+ spins in Eu 3+ :Y 2 SiO 5

In this paper, we present a method to investigate and control the dynamics of the nearby host nuclear spins (the 'frozen core') about a rare-earth ion doped in a crystal. Optically detected, double quantum magnetic resonance measurements were conducted on Eu3+ $:$ Y2SiO5. The distinct magnetic resonant frequencies of nearby Y3+ spins were measured along with the lifetime and coherence time of an individual Y3+ spin. We demonstrate an entangling gate between the Eu3+ spins and a Y3+ spin associated with a particular position. Further, we propose a method to initialize the Y3+ spin states, enabling the Y3+ spins to be used as a quantum resource for quantum information applications.This work was supported by the Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology (Grant No. CE110001027). MZ is supported by the Science, Technology and Innovation Commission of Shenzhen Municipality (No. ZDSYS20170303165926217, No. JCYJ20170412152620376)) and Guangdong Innovative and Entrepreneurial Research Team Program (Grant No. 2016ZT06D348). RLA is a recipient of an Australian Research Council Discovery Early Career Researcher Award (project No. DE170100099)

Technique for frequency selective, sub-diffraction limited imaging of rare-earth ions in bulk crystals

We propose and demonstrate the principle of a sub-diffraction-limited optical imaging technique for rare-earth ion crystals that preserves the ions’ homogeneous line width. Our method uses a combination of applied electric field gradients and optical pumping to create a resonant nanoscopic volume within an otherwise non-resonant macroscopic crystal. We present the concept of the Stark activation technique and perform a demonstration in Pr³⁺: Y₂SiO₅ in which we create a 10 μm-thick absorption feature in a 1 mm thick crystal. By modeling the system we show that it is possible to increase the resolution of the technique to the 5 nm range for single Pr³⁺ ions. We also discuss the physical properties that will fundamentally limit the resolution of Stark activation. Because the proposed technique simultaneously achieves high spatial and high spectral resolution it is an enabling protocol to realize technology based on single rare-earth ions and harness short-range interactions in ensembles.This work was supported by the Australian Research Council Center of Excellence for Quantum Computation and Communication Technology (CE110001027). M.J.S. was supported by an Australian Research Council Future Fellowship (FT110100919)

Non-classical photon streams using rephased amplified spontaneous emission

We present a fully quantum mechanical treatment of optically rephased photon echoes. These echoes exhibit noise due to amplified spontaneous emission, however this noise can be seen as a consequence of the entanglement between the atoms and the output light. With a rephasing pulse one can get an "echo" of the amplified spontaneous emission, leading to light with nonclassical correlations at points separated in time, which is of interest in the context of building wide bandwidth quantum repeaters. We also suggest a wideband version of DLCZ protocol based on the same ideas.Comment: 5 pages, 4 figures. Added section