Building a secure quantum internet

A quantum internet is a radically new technology that can connects (quantum) devices, such as quantum computers, over large distances. This will allow for novel innovations, including levels of privacy, security and computation power that are impossible to achieve with today’s internet. At QuTech, our mission is to provide the enabling technology for the future quantum internet and showcase the very first fully functional quantum networks.

We are unique in that we’re working on every single aspect necessary for realizing quantum networks: we’re developing the software, the interface between software and hardware, and the hardware.  

Quantum network protocols and applications

Long-term goal: 

To develop a full quantum network stack and novel applications for a quantum internet.

Highlights:

  • Through a joint research and engineering effort, we were the first in the world to demonstrate a full quantum network stack on an experimental NV hardware platform developed within the division. A scientific manuscript describing this work is currently under review (arXiv). This represents a key milestone towards a full control stack for the quantum internet.

  • We released NetSquid, which is a unique quantum network simulator, to simulate entanglement distribution over a 1000-node repeater chain in <2 seconds, and a control-plane of a quantum switch beyond the analytically known regime (Communications Physics).

  • We developed a novel variational algorithm to identify near-optimal probes and measurement operators for noisy multi-parameter estimation problems in quantum networks, and demonstrated the practical functioning of the approach through numerical simulations (npj Quantum Information)

Quantum network hardware

Long-term goal: 

Experimental demonstrations that push the frontier of quantum networking hardware and yield new enabling technologies and insights.

Highlights:

  • We realized the world’s first multimode entanglement-based quantum network. We demonstrated the distribution of multipartite entanglement as well as entanglement swapping without post-selection. Our results establish a new and unique testbed for exploring and testing quantum network protocols and for developing a quantum network control stack (Science).

  • We realized coupling between an NV centre and an open microcavity, which can potentially boost the entanglement generation rates of NV-based quantum networks significantly. We observed Purcell enhancement of the transition and demonstrated for the first time resonant optical excitation as well as collection of the NV centre inside a cavity (Phys. Rev. Applied).

  • We demonstrated quantum interference between photons, converted to telecom wavelength, coming from two separated and independent NV nodes in the lab (arXiv). We measured a visibility of 0.79, and showed stable operation of the nodes over a consecutive period of multiple days. 

  • We continued the development of quantum repeater nodes based on rare-earth atoms demonstrating their great potential for multiplexed operation. In particular, we found optical coherence times in thulium-doped yttrium gallium garnet (Tm:Y3Ga5O12; Tm:YGG) at a temperature of 500 mK in excess of 1 ms, and demonstrated storage of optical pulses for periods up to 100 ms. This is the longest storage time in optical coherence of rare-earth-doped crystals reported to date, and constitutes an almost 3 orders of magnitude improvement compared to our previous best (Phys. Rev. Lett.).

Quantum processors for quantum networks

Long-term goal: 

To develop and exploit multi-qubit quantum processors for use in a quantum internet and networked computing.

Highlights:

  • We experimentally observed a discrete time crystal, a new intrinsically out-of-equilibrium phase of matter that spontaneously breaks time translation symmetry (Science).  For this we realized a 1D chain of 9 spin qubits in diamond (C13 nuclear spins). This result highlights the potential of using our quantum processors for quantum simulations of many-body physics, one of the most promising NISQ-type applications for quantum computation and simulation.

  • We demonstrated how error-correction can be employed to further enhance qubit performance. We experimentally realized a complete logical qubit of an error correction code and demonstrated that we could operate this logical qubit fault-tolerantly (arXiv). This work provided the first demonstration of fault-tolerance with a logical qubit based on solid-state qubits, achieved a few months earlier with ion traps – a key milestone in spin-based and solid-state quantum computation. Together with advances in optical entanglement links, this work also lays the foundation for distributed quantum error correction in modular quantum computers.