Session R62: Noisy Intermediate-Scale Quantum Computers

Quantum Computing in the NISQ era and beyond

Noisy Intermediate-Scale Quantum (NISQ) technology will be available in the near future. Quantum computers with 50-100 qubits may be able to perform tasks which surpass the capabilities of today's classical digital computers, but noise in quantum gates will limit the size of quantum circuits that can be executed reliably. NISQ devices will be useful tools for exploring many-body quantum physics, and may have other useful applications, but the 100-qubit quantum computer will not change the world right away --- we should regard it as a significant step toward the more powerful quantum technologies of the future. Quantum technologists should continue to strive for more accurate quantum gates and, eventually, fully fault-tolerant quantum computing.   

Advances in quantum simulation on the path towards post-supremacy, pre-fault-tolerant applications

Quantum simulation looks to be one of those most promising applications for near-term quantum computers. However, even in an optimistic mindset, it is clear that utilizing a post-supremacy device for near-term applications will present a number of challenges. To date, the maximum number of utilized qubits for such applications is significantly smaller than a post-supremacy device, and direct application of previous methods with no modifications could simply prohibit more qubits from giving a better or more interesting answer. In this talk I will discuss some of these challenges and recent advances in both the algorithms for simulating these problems with lower overheads and mitigating some of these difficulties directly.   

Simple tricks to squeeze more out of your noisy quantum device

Near-term applications of early quantum devices rely on accurate estimates of expectation values to become relevant. Decoherence and gate errors lead to wrong estimates. This problem was, at least in theory, remedied with the advent of quantum error correction. However, the overhead that is needed to implement a fully fault-tolerant gate set with current codes and current devices seems prohibitively large. In turn, steady progress is made in improving the quality of the quantum hardware and we believe that we can build machines in the near term that cannot be emulated by a conventional computer. We discuss simple techniques that increase the quality of short-depth quantum simulations. In light of these advances, it becomes interesting to ask what these noisy devices can be used for. In this talk we will present our advances in the search for quantum algorithms for noisy quantum computers that may be relevant to problems in quantum simulation and quantum machine learning.   

Photonic quantum networks

Hybrid light-matter networks offer the promise for delivering robust quantum information processing technologies, from sensor arrays to quantum simulators. Recent develpoments in new quantum light sources, reconfigurable and modular circuit design and fabrciation, novel waveguide-based detectors and low-noise photonic memories have all contributed in progress towards a resilient, scalable photonic quantum network. Purely photonic quantum simulators have been demonstrated, and better understanding of the role of imperfections in degrading the performance of such devices has been made, alghouth concrete limits are known in only a few cases. Meanwhile progress in hybrid networks indicates that scalable performance should be possible, albeit only when a number of engineering challenges have been met.

  

Scaling Ion-trap Quantum Computing

Scalability is tied to the notion of being able to take individual components, combine an increasing number of these components, and be able to predict the performance of the larger system from its constituents. Verifying scalability is thus tied to routines that allow us to both investigate the performance of building blocks as well as larger systems. In this presentation I will present recent work on investigating the performance of the Innsbruck-based ion-trap quantum computer as the quantum register size increases, provide an ongoing project to extend quantum error correction capabilities including loss and outline changes to the apparatus to push towards a 20-qubit quantum processor with parallel processing capabilities.