High Resolution Spectroscopy of Erbium Doped Solids

This thesis investigates the potential of Er:YSO and Er:Si for quantum communication and computation applications. Erbium uniquely possess optical transitions in the 1.5 um region, making it suitable for both fibre telecommunication and silicon photonics. The properties of the ${I}_{15/2}\leftrightarrow{I}_{13/2}$ optical transition in Er:YSO have already been extensively studied. Over two decades ago, improvements in $Er^{3+}$ dephasing time at 1.5 um were achieved by applying a 5T field along the D1 axis. More recently, a record 4.4 ms coherence time on the same optical transition was achieved using a 7T field. These investigations, among others, illustrate that large Er electron spins become thermally polarised with sufficient magnetic field. However, no long lived and coherent spin transitions associated with the Er ions had previously been identified, and such transitions are necessary for on-demand quantum state storage. To address this requirement, the optical and hyperfine transition properties of 167-Er:YSO were investigated in large magnetic fields. In a field of 7T, spectral hole lifetimes of 1 minute and hyperfine population lifetimes of 12 minutes were observed. These measurements illustrate the effect of spin-lattice relaxation in this system, and how it can be mitigated. Efficient spin-polarisation of the entire 167-Er hyperfine ensemble is also demonstrated. This is the first such demonstration in rare earth systems, and a key requirement for broadband optical storage. Moreover, a 1.3 second coherence time was recorded for an 167-Er:YSO hyperfine transition at 7T and 1.4 K. This is an improvement of several orders-of-magnitude over previous coherence measurements on spin-transitions in Er doped solids. This is also sufficient for maximal entanglement rates in quantum repeater networks that span distances of 1000 km or greater. With an optical transition at 1.5 um, Er is also an ideal candidate to connect silicon based quantum computers to the future quantum Internet. In particular, single Er:Si ions could be used to develop an optical-spin bus between P:Si qubits and fibre based quantum networks. Presented here is the first spectroscopic investigation of single Er:Si ions. This required a novel opto-electronic approach to single ion detection, where the Er ions are implanted into a nanometre scale fin-shaped Field Effect Transistor. With this approach it was possible to develop high resolution optical spectra, where both the electronic and hyperfine levels of individual Er ions were resolved. Long optical and spin coherence times are also important requirements for an optical-spin bus. To address the first requirement, an investigation of the optical lineshape was undertaken. Here it was determined that sources of Stark noise external to the transistor channel contribute a significant amount to optical homogeneous linewidth. However, the dominant noise contribution was determined to be short-range (from within the 30 nm wide channel) and the total homogeneous linewidth was measured to be 50 MHz. The site structure of an individual Er:Si ion was then analysed, using magnetic field rotation patterns and optical transitions between multiple crystal field levels. This site was determined to have approximately axial ($C_{3}$) symmetry. The purpose of this study was to determine a magnetic field regime in which the Er electrons spin can be polarised, which is necessary for realising of long hyperfine lifetimes and coherence times

Spatial mode storage in a gradient echo memory

Three-level atomic gradient echo memory (lambda-GEM) is a proposed candidate for efficient quantum storage and for linear optical quantum computation with time-bin multiplexing. In this paper we investigate the spatial multimode properties of a lambda-GEM system. Using a high-speed triggered CCD, we demonstrate the storage of complex spatial modes and images. We also present an in-principle demonstration of spatial multiplexing by showing selective recall of spatial elements of a stored spin wave. Using our measurements, we consider the effect of diffusion within the atomic vapour and investigate its role in spatial decoherence. Our measurements allow us to quantify the spatial distortion due to both diffusion and inhomogeneous control field scattering and compare these to theoretical models.Comment: 11 pages, 9 figure

Optical addressing of an individual erbium ion in silicon

The detection of electron spins associated with single defects in solids is a critical operation for a range of quantum information and measurement applications currently under development. To date, it has only been accomplished for two centres in crystalline solids: phosphorus in silicon using electrical readout based on a single electron transistor (SET) and nitrogen-vacancy centres in diamond using optical readout. A spin readout fidelity of about 90% has been demonstrated with both electrical readout and optical readout, however, the thermal limitations of the electrical readout and the poor photon collection efficiency of the optical readout hinder achieving the high fidelity required for quantum information applications. Here we demonstrate a hybrid approach using optical excitation to change the charge state of the defect centre in a silicon-based SET, conditional on its spin state, and then detecting this change electrically. The optical frequency addressing in high spectral resolution conquers the thermal broadening limitation of the previous electrical readout and charge sensing avoids the difficulties of efficient photon collection. This is done with erbium in silicon and has the potential to enable new architectures for quantum information processing devices and to dramatically increase the range of defect centres that can be exploited. Further, the efficient electrical detection of the optical excitation of single sites in silicon is a major step in developing an interconnect between silicon and optical based quantum computing technologies.Comment: Corrected the third affiliation. Corrected one cross-reference of "Fig. 3b" to "Fig. 3c". Corrected the caption of Fig. 3a by changing (+-)1 to

Single rare-earth ions as atomic-scale probes in ultra-scaled transistors

Continued dimensional scaling of semiconductor devices has driven information technology into vastly diverse applications. As the size of devices approaches fundamental limits, metrology techniques with nanometre resolution and three-dimensional (3D) capabilities are desired for device optimisation. For example, the performance of an ultra-scaled transistor can be strongly influenced by the local electric field and strain. Here we study the spectral response of single erbium ions to applied electric field and strain in a silicon ultra-scaled transistor. Stark shifts induced by both the overall electric field and the local charge environment are observed. Further, changes in strain smaller than $3\times 10^{-6}$ are detected, which is around two orders of magnitude more sensitive than the standard techniques used in the semiconductor industry. These results open new possibilities for non-destructive 3D mapping of the local strain and electric field in the channel of ultra-scaled transistors, using the single erbium ions as ultra-sensitive atomic probes.Comment: 10+5 pages, 4+3 figure

Coherence time of over a second in a telecom-compatible quantum memory storage material

Quantum memories for light will be essential elements in future long-range quantum communication networks. These memories operate by reversibly mapping the quantum state of light onto the quantum transitions of a material system. For networks, the quantum coherence times of these transitions must be long compared to the network transmission times, approximately 100 ms for a global communication network. Due to a lack of a suitable storage material, a quantum memory that operates in the 1,550nm optical fibre communication band with a storage time greater than 1 mu s has not been demonstrated. Here we describe the spin dynamics of Er-167(3+):Y2SiO5 in a high magnetic field and demonstrate that this material has the characteristics for a practical quantum memory in the 1,550nm communication band. We observe a hyperfine coherence time of 1.3 s. We also demonstrate efficient spin pumping of the entire ensemble into a single hyperfine state, a requirement for broadband spin-wave storage. With an absorption of 70 dB cm(-1) at 1,538 nm and Lambda transitions enabling spin-wave storage, this material is the first candidate identified for an efficient, broadband quantum memory at telecommunication wavelengths

Parkes Weber syndrome-diagnostic and management paradigms: a systematic review

Objectives Parkes Weber syndrome is a congenital vascular malformation which consists of capillary malformation, venous malformation, lymphatic malformation, and arteriovenous malformation. Although Parkes Weber syndrome is a clinically distinctive entity with serious complications, it is still frequently misdiagnosed as Klippel-Trenaunay syndrome that consists of the triad capillary malformation, venous malformation, and lymphatic malformation. Methods We performed a systematic review investigating clinical, diagnostic, and treatment modalities of Parkes Weber syndrome (PubMed/MEDLINE, Embase, and Cochrane databases). Thirty-six publications (48 patients) fulfilled the eligibility criteria. Results The median age of patients was 23 years (IQR, 8-32), and 24 (50.0%) were males. Lower extremity was affected in 42 (87.5%) and upper extremity in 6 (12.5%) patients; 15 (31.3%) patients developed high-output heart failure; 12 (25.0%) patients had chronic venous ulcerations, whereas 4 (8.3%) manifested distal arterial ischemia. The spinal arteriovenous malformations were reported in six (12.5%) patients and coexistence of aneurysmatic disease in five (10.4%) patients. The most frequently utilized invasive treatments were embotherapy followed by amputation and surgical arteriovenous malformation resection, and occasionally stent-graft implantation. All modalities showed clinical improvement. However, long follow-up and outcome remained unclear. Conclusion A diagnosis of Parkes Weber syndrome should be made on the presence of capillary malformation, venous malformation, lymphatic malformation, and arteriovenous malformation (as main defect) in overgrowth extremity. Arteriovenous malformation presents the criterion for distinguishing Parkes Weber syndrome from Klippel-Trenaunay syndrome, which is substantial for treatment strategy. The primary management goal should be patient's quality of life improvement and complication reduction. Embolization alone/combined with surgical resection targeting occlusion or removal of arteriovenous malformation "nidus" reliably leads to clinical improvement

Assessing the potential of para-donor and para-acceptor substituted 5-benzylidenebarbituric acid derivatives as push-pull electronic systems: Experimental and quantum chemical study

Electronic interactions in donor-pi-linker-acceptor systems with barbituric acid as an electron acceptor and possible electron donor were investigated to screen promising candidates with a push-pull character based on experimental and quantum chemical studies. The tautomeric properties of 5-benzylidenebarbituric acid derivatives were studied with NMR spectra, spectrophotometric determination of the pKa values, and quantum chemical calculations. Linear solvation energy relationships (LSER) and linear free energy relationships (LFER) were applied to the spectral data - UV frequencies and C-13 NMR chemical shifts. The experimental studies of the nature of the ground and excited state of investigated compounds were successfully interpreted using a computational chemistry approach including ab initio MP2 geometry optimization and time-dependent DFT calculations of excited states. Quantification of the push-pull character of barbituric acid derivatives was performed by the (CNMR)-C-13 chemical shift differences, Mayer pi bond order analysis, hole-electron distribution analysis, and calculations of intramolecular charge transfer (ICT) indices. The results obtained show, that when coupled with a strong electron-donor, barbituric acid can act as the electron-acceptor in push-pull systems, and when coupled with a strong electron-acceptor, barbituric acid can act as the weak electron-donor

Spatial-mode storage in a gradient-echo memory

Three-level atomic gradient echo memory (Λ-GEM) is a proposed candidate for efficient quantum storage and for linear optical quantum computation with time-bin multiplexing. In this paper we investigate the spatial multimode properties of a Λ-GEM system