### Quantum plasmonics

Integrated systems using surface plasmons offer great potential for use in quantum state engineering applications, such as single-photon sources and transistors (important for quantum communication and computing). Here, novel capabilities in the way the electromagnetic field can be localized and manipulated offer the prospect of miniaturization, scalability and strong coherent coupling to single emitter systems that conventional photonics cannot achieve.

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**Selected publications:**

*Single-Photon Excitation of Surface Plasmon Polaritons**Quantum Statistics of Surface Plasmon Polaritons in Metallic Stripe Waveguides**Long-range surface-plasmon-polariton excitation at the quantum level**Quantum theory of surface-plasmon polariton scattering**Quantum plasmonics with a metallic nanoparticle array**Observation of Quantum Interference in the Plasmonic Hong-Ou-Mandel Effect**Quantum plasmonic excitation in graphene and loss-insensitive propagation*

**Dealing with loss:**

**Metamaterials:
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*Tunable negative permeability in a quantum plasmonic metamaterial**Quantum entanglement distillation with metamaterials**Experimental distillation of photon entanglement using a plasmonic metamaterial*

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### Optical cluster state quantum computing

Multipartite entangled states, called cluster states (or graph states), can be used as resources to perform quantum computing. Here, the amount of control one needs over a quantum system is reduced to the ability of performing just single-qubit measurements. This is an important advantage over competing computational models for a number of physical systems, most notably those using photons.

Selected publications:

*Experimental realization of Deutsch’s algorithm in a one-way quantum computer**Scalable method for demonstrating the Deutsch-Jozsa and Bernstein-Vazirani algorithms using cluster states**Hybrid cluster state proposal for a quantum game**Natural three-qubit interactions in one-way quantum computing**Compact Toffoli gate using weighted graph states**Experimental Realization of a One-way Quantum Computer Algorithm Solving Simon’s Problem*

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### Quantum computing on superconducting processors

While our main research focus is on quantum photonic systems, we are also interested in testing protocols on more advanced quantum systems using superconducting circuitry, such as those available from IBM. These systems are among the current front-runners for quantum information processing in the noisy intermediate-scale quantum (NISQ) regime.

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**Selected publications:**

*Demonstration of Shor’s factoring algorithm for N=21 on IBM quantum processors**Implementation of single-qubit measurement-based t-designs using IBM processors*

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### New types of single-photon source

Improving photon generation rates using new types of sources, such as photonic crystal fibres, and understanding better the practical requirements for generating high-quality entanglement between these sources will open up access to larger entangled states with more complex structures than currently available. This would enable the testing of quantum protocols and probing physical phenomena that only more sizable quantum systems are able to support.

**Selected publications:**

*Experimental characterization of photonic fusion using fiber sources**Experimental characterization of universal one-way quantum computing*

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### Quantum networking

Symmetries within entangled states make them suitable resources for carrying out quantum networking protocols, such as telecloning, open-destination teleportation and quantum secret sharing. Some of these have recently been demonstrated in four- and six-photon settings.

**Selected publications:**

*Experimental Realization of Dicke States of up to Six Qubits for Multiparty Quantum Networking**Characterizing multipartite symmetric Dicke states under the effects of noise**Universal gates for transforming multipartite entangled Dicke states**Fusing multiple W states simultaneously with a Fredkin gate**Experimental demonstration of graph-state quantum secret sharing*

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### Decoherence protection

Decoherence is the ubiquitous loss of information encoded in a quantum system due to its uncontrollable interaction with an environment. It is one of the main obstacles in the grounding of quantum technology for massively parallel information processing. The design and testing of fault-tolerant protocols counteracting the effects of decoherence is necessary for the achievement of reliable quantum information processing.

**Selected publications:**

*One-way quantum computing in a decoherence-free subspace**Experimental demonstration of decoherence-free one-way information transfer**Decoherence-based exploration of d-dimensional one-way quantum computation**Experimental demonstration of a graph state quantum error-correction code*

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### In the Media

- First use of Deutsch’s algorithm in a cluster state quantum computer – PhysOrg.com (2007)
- A quantum renaissance – Physics World (2008)
- Tricking the perfect code machine – BBC news (2011)
- Quantum graph code – NdabaOnline (2014)
- Historic quantum software is run for the first time – New Scientist (2014)
- Milestone algorithm runs on quantum computer – Science News (2014)
- Algorithm runs faster on quantum computer – Physics Today (2014)
- Simon says quantum computing will work – The Register (2014)
- A continent works to grow its stake in quantum computing – World University News (2020)
- Helping SA make a quantum leap into digital future (MSc students) – The Star (2021)
- IBM working with students to make South Africa Quantum ready (MSc students) – Hypertext (2021)
- South Africa’s Progress in becoming Quantum Ready begins with empowering the youth (MSc students) – Tech Smart (2021)
- South Africa’s progress in becoming quantum ready – IBM Research blog (2021)
- Who’s to say it’s impossible to build your own quantum processor – The Newspaper (2021)

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### Outreach

- IKEA quantum cryptography booklet for a stall at Imperial’s Science of secrecy public event (2011)

[Visit Nic’s twitter feed for more science outreach stuff!]