Trusted Computing and the Challenges of Cryptographic Algorithms in Quantum Computing

Military & Aerospace Electronics

Published in Military & Aerospace Electronics

At its core, quantum computing is very different from a traditional computer. The quantum computer operates on qubits, using quantum gates and measurements, rather than operating on bits per a Von Neuman architecture -- using memory and a processing unit made up of digital gates.

A qubit is not binary. It does not simply encode a 1 or a 0 as a bit does. Instead, a set of n qubits encodes a superposition of 2^n possible quantum states. This means that while a traditional digital computer operating on 32-bits only can process one 32-bit value at any given time, a quantum computer with 32-qubits can look simultaneously at the probabilities of all possible 32-bit value combinations.

Quantum computing has several challenges. A quantum computer processes a particular algorithm by configuring the set of quantum gates and initializing the values of the qubits. Taking a measurement causes the quantum states to resolve, and users can measure an actual state of the qubits. For example, once the quantum states resolve in a 32-qubit system, it is no longer in an unknown set of the 2^32 possible combinations but has resolved to a single possible solution.

Because a quantum computer works with quantum states, each value is often only probabilistic in nature. Normally, to determine a result with sufficient accuracy, a quantum computer runs several times, re-initializing the system, configuring qubits, and then measuring a state. Each subsequent measurement records as a potential result. Users then can analyze these sets of results to determine which of the results most likely are correct.

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