«Letters from the old country»: exploring and defining Ukrainian Canadian vernacular letter writing

У тезах розглянуто феномен україномовного листування в середовищі української еміграції в Канаді. Проаналізовано тенденції до збереження рідної мови у чужому соціокультурному оточенні на основі листів між самими емігрантами та їх родичами на материковій Україні. Автором виокремлено та досліджено різні періоди у розвитку україномовного листування емігрантів, його значення у збереженні власної національної самоідентичності. (The article considers the phenomenon of Ukrainian correspondence of the Ukrainian emigration society in Canada. Taking into consideration letters among the emigrants themselves and their relatives on mainland Ukraine, the author analyses tendencies to preserve their native language in foreign social and cultural environment. Moreover, the author singles out and examines various development periods of Ukrainian emigrants’ correspondence and its importance in preserving their national identity.

Adiabatic two-qubit gates in capacitively coupled quantum dot hybrid qubits

The ability to tune qubits to flat points in their energy dispersions ("sweet spots") is an important tool for mitigating the effects of charge noise and dephasing in solid-state devices. However, the number of derivatives that must be simultaneously set to zero grows exponentially with the number of coupled qubits, making the task untenable for as few as two qubits. This is a particular problem for adiabatic gates, due to their slower speeds. Here, we propose an adiabatic two-qubit gate for quantum dot hybrid qubits, based on the tunable, electrostatic coupling between distinct charge configurations. We confirm the absence of a conventional sweet spot, but show that controlled-Z (CZ) gates can nonetheless be optimized to have fidelities of $\sim$99% for a typical level of quasistatic charge noise ($\sigma_\varepsilon$$\simeq$1 $\mu$eV). We then develop the concept of a dynamical sweet spot (DSS), for which the time-averaged energy derivatives are set to zero, and identify a simple pulse sequence that achieves an approximate DSS for a CZ gate, with a 5$\times$ improvement in the fidelity. We observe that the results depend on the number of tunable parameters in the pulse sequence, and speculate that a more elaborate sequence could potentially attain a true DSS.Comment: 14 pages, 9 figure

Spin Readout and Initialization in a Semiconductor Quantum Dot

Electron spin qubits in semiconductors are attractive from the viewpoint of long coherence times. However, single spin measurement is challenging. Several promising schemes incorporate ancillary tunnel couplings that may provide unwanted channels for decoherence. Here, we propose a novel spin-charge transduction scheme, converting spin information to orbital information within a single quantum dot by microwave excitation. The same quantum dot can be used for rapid initialization, gating, and readout. We present detailed modeling of such a device in silicon to confirm its feasibility.Comment: Published versio