One step closer to scalable photonic quantum computing

Ulrik L. Andersen

Debarka Mukhopadhyay, Siddhartha Bhattacharyya, Jan Platoš +3 more

Jean-Luc Tambasco

This thesis investigates quantum photonic technology, proposing novel designs and photonic components towards the next generation of quantum computing and information processing. Chapter 1 introduces the history and motivation behind quantum information, and evaluates today’s most promising quantum technology platforms. Chapter 2 provides an overview of requisite linear and nonlinear classical photonic theory, introduces topological photonics and quantum photonic concepts, as well as nanofabrication principles. In chapter 3, a published novel probabilistic single photon source design is proposed, aimed at improving yield and photon purity. Chapter 4 proposes a published novel scheme for manipulating photons with the goal of enabling robust new quantum photonic gate designs. Chapter 5 introduces two works investigating a new photonic platform, lithium niobate on insulator (section 5.1), suitable for quantum photonic technology, and demonstrates the initial steps towards the development of spectral filtering on this platform (section 5.2). This thesis seeks to explore and advance future quantum photonic technology, from sources design to quantum photonic gate design and fabrication, stepping closer to the long standing dream of scalable photonic quantum computing.

Marco Riccardi, Roberto Menta, Francesco Cioni +3 more

We propose a platform to implement a scalable universal quantum computer based on a 2D array of superconducting qubits. Notably, calculations in our scheme are enabled by a set of only three global driving signals, irrespective of the number of qubits, ensuring full scalability of the computation. In stark contrast with the existing literature, global control in our scheme is achieved by leveraging the longitudinal ZZ coupling between neighboring qubits. We show how this enables information flow, one-and two-qubit gates through a series of three global pulses that act together on different subsets of the physical qubits in our system. These findings provide an alternative route to the realization of scalable and fault-tolerant superconducting quantum computers with reduced wiring, bringing them one step closer to solving practical problems in our daily lives.

Rohit Chaurasiya, Devanshi Arora

S. Omkar, Seok-Hyung Lee, Yong Siah Teo +2 more

Linear optical quantum computing is beset by the lack of deterministic entangling operations besides photon loss.Motivated by advancements at the experimental front in deterministic generation of various kinds of multiphoton entangled states, we propose an architecture for linear-optical quantum computing that harnesses the availability of three-photon Greenberger-Horne-Zeilinger (GHZ) states.Our architecture and its subvariants use polarized photons in GHZ states, polarization beam splitters, delay lines, optical switches, and on-off detectors.We concatenate the topological quantum error-correction code with three-qubit repetition codes and estimate that our architecture can tolerate a remarkably high photon-loss rate of 11.5%; this makes a drastic change that is at least an order higher than those of known proposals.Furthermore, considering three-photon GHZ states as resources, we estimate the resource overheads to perform gate operations with an accuracy of 10 -6 (10 -15 ) to be 2.07 × 10 6 (5.03 × 10 7 ).Compared to other all-photonic schemes, our architecture is also resource efficient.In addition, the resource overhead can be even further improved if larger GHZ states are available.Given its striking enhancement in the photon-loss threshold and the recent progress in generating multiphoton entanglement, our scheme moves scalable photonic quantum computing a step closer to reality.