Quantum computers will finally be useful: what’s behind the revolution

Adam Becker

Joshua

Jie Sun, Songfeng Lu, Li Li

It is known that when the initial state has no overlap with the final state in an adiabatic computation, an extra assisted driving Hamiltonian has to be used to avoid the failure of quantum adiabatic algorithm. This assisted Hamiltonian has a relatively fixed form, which can be seen in the related literature but the mechanism behind it is still not clear enough. In this paper, we discuss the usefulness of a generalized form of assisted driving Hamiltonian in adiabatic evolution which may shed light on this problem.

Anand Choudhary, Ajay Wasan

With the nature-powered quantum revolution gaining momentum, Quantum Computation and Quantum Information are all set to transform the landscape of all areas of science and technology. Quantum Cryptography is one such field which has witnessed tremendous progress in theory as well as in its practical implementation. Quantum Key Distribution is one of its integral parts and it necessarily requires the usage of an information reconciliation protocol to correct the errors present in the key bits transmitted via the physical system involved. Cascade is one such protocol which enjoys popularity among such system developers due to its simplicity and high error-correction efficiency. In this work, we identify, improve, interpret, and implement key optimizations from a practical viewpoint and give an algorithmic implementation of the Cascade protocol which would serve to increase its overall efficiency without changing its foundational structure. We also dig deep into the math and physical interpretation behind the values and expressions of key parameters and quantities of Cascade, which effectively make use of the cascade of errors unearthed by it so as to not only ensure an exponentially decreasing probability of any errors in the key bits with the passes of Cascade but also ensure that only the minimum possible information is leaked to a potential eavesdropper. Finally, we also give a visual walk-through of Cascade in action and support it with explanations at every step. By doing so, we aim to equip researchers and developers with an insight driven error correction tool which is sure to be useful in practice.

Jeff Kabachinski

Zhenghan Wang

Although the current information revolution is still unfolding, the next industrial revolution is already rearing its head. A second quantum revolution based on quantum technology will power this new industrial revolution with quantum computers as its engines. The development of quantum computing will turn quantum theory into quantum technology, hence release the power of quantum phenomena, and exponentially accelerate the progress of science and technology. Building a large-scale quantum computing is at the juncture of science and engineering. Even if large-scale quantum computers become reality, they cannot make the conventional computers obsolete soon. Building a large-scale quantum computer is a daunting complex engineering problem to integrate ultra-low temperature with room temperature and micro-world with macro-world. We have built hundreds of physical qubits already but are still working on logical and topological qubits. Since physical qubits cannot tolerate errors, they cannot be used to perform long precise calculations to solve practically useful problems yet.