Practice quantum computing roadmap vocabulary: NISQ era, fault-tolerant quantum computing, quantum advantage demonstration, beyond classical, and quantum volume metric.
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What is the 'NISQ era' in quantum computing?
NISQ (coined by John Preskill) describes today's quantum computers: they have enough qubits to potentially do interesting things, but their noise levels prevent running the deep circuits needed for full fault-tolerant algorithms. Finding useful NISQ algorithms is an active research area.
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What does a 'quantum advantage demonstration' claim?
A quantum advantage demonstration shows a quantum computer outperforming classical computers on a specific task. These demonstrations (like Google's 2019 random circuit sampling experiment) are important milestones, though debate often follows about whether the classical comparison is fair.
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What does 'quantum volume' measure?
Quantum Volume (QV) is a single-number benchmark that accounts for qubit count, gate fidelity, qubit connectivity, and measurement errors together. A QV of 128 means the computer can reliably execute random circuits of 7 qubits and 7 layers deep (2^7=128).
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What does 'beyond classical' mean in quantum computing announcements?
'Beyond classical' describes a result where classical simulation of the quantum computation becomes intractable. It is similar to 'quantum supremacy' but often used when the task may not be practically useful — just demonstrating that the quantum device is doing something classically hard.
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What is 'fault-tolerant quantum computing' and how does it differ from NISQ computing?
Fault-tolerant quantum computing (FTQC) encodes logical qubits in many physical qubits and uses error correction to suppress errors below detectable levels. This enables deep circuit execution required for algorithms like Shor's. NISQ devices lack sufficient qubit quality/count for this.