arXiv subjects

Christopher J. Ballance

Publications and source records attributed to Christopher J. Ballance.

3 recordsLinked to original sources

arXiv2026

Applications of Spin-Dependent Generalized Squeezing in Hybrid Spin-Oscillator Quantum Processors

Generalized squeezing interactions are foundational to quantum optics, and have recently come under experimental control in hybrid spin-oscillator quantum processors [O. Băzăvan, et al., Nat. Phys. 22, 757 (2026); S. Saner, et al., Phys. Rev. X 16, 021049 (2026)]. These interactions open the door for new applications in the processing of discrete- and continuous-variable quantum information, four of which we propose and investigate in this work: geometric phase gates mediated by spin-dependent generalized squeezing acting on two spins and a common oscillator; genuine N-body spin interactions mediated by individually addressed spin-dependent generalized squeezing; oscillator thermometry via spin readout; and the preparation of high-fidelity quantum states of the oscillator via spin-dependent generalized squeezing and mid-circuit measurement. A unifying feature of these applications is the geometric phase induced by generalized squeezing interactions, which is nonlinear in the Fock occupation of the oscillator and the interaction order of the generalized squeezing. This work provides a foundation for fast, high-fidelity discrete- and continuous-variable quantum computation and sensing in the hybrid spin-oscillator platform via generalized squeezing.

quant-ph↗

arXiv2018

A short response-time atomic source for trapped ion experiments

Ion traps are often loaded from atomic beams produced by resistively heated ovens. We demonstrate an atomic oven which has been designed for fast control of the atomic flux density and reproducible construction. We study the limiting time constants of the system and, in tests with $^{40}\textrm{Ca}$, show we can reach the desired level of flux in 12s, with no overshoot. Our results indicate that it may be possible to achieve an even faster response by applying an appropriate one-off heat treatment to the oven before it is used.

physics.atom-ph↗

arXiv2016

Minimally complex ion traps as modules for quantum communication and computing

Optically linked ion traps are promising as components of network-based quantum technologies, including communication systems and modular computers. Experimental results achieved to date indicate that the fidelity of operations within each ion trap module will be far higher than the fidelity of operations involving the links; fortunately internal storage and processing can effectively upgrade the links through the process of purification. Here we perform the most detailed analysis to date on this purification task, using a protocol which is balanced to maximise fidelity while minimising the device complexity and the time cost of the process. Moreover we 'compile down' the quantum circuit to device-level operations including cooling and shutting events. We find that a linear trap with only five ions (two of one species, three of another) can support our protocol while incorporating desirable features such as 'global control', i.e. laser control pulses need only target an entire zone rather than differentiating one ion from its neighbour. To evaluate the capabilities of such a module we consider its use both as a universal communications node for quantum key distribution, and as the basic repeating unit of a quantum computer. For the latter case we evaluate the threshold for fault tolerant quantum computing using the surface code, finding acceptable fidelities for the 'raw' entangling link as low as 83% (or under 75% if an additional ion is available).

quant-ph↗