Computer Science Grade 12 20 min

Quantum Computing Intro

Quantum Computing Intro

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1

Introduction & Learning Objectives

Learning Objectives Define a qubit and contrast it with a classical bit. Explain the concepts of superposition and entanglement using analogies. Represent a qubit's state mathematically using Dirac notation (e.g., α|0⟩ + β|1⟩). Calculate the probability of measuring a qubit in a specific state from its probability amplitudes. Trace the state of a qubit through a basic quantum gate like the Hadamard gate. Identify the types of computational problems where quantum computers offer a significant advantage. What if a computer bit could be both 0 and 1 at the same time? 🤯 This isn't science fiction; it's the foundation of quantum computing. This lesson introduces the fundamental principles of quantum computing, a revolutionary paradigm that leverages quantum mecha...
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Key Concepts & Vocabulary

TermDefinitionExample Qubit (Quantum Bit)The fundamental unit of quantum information. Unlike a classical bit, which must be either 0 or 1, a qubit can exist in a combination of both states simultaneously.Imagine a spinning coin. Before it lands, it's not definitively heads or tails—it's in a state that encompasses both possibilities. A qubit is similar, holding the potential for both 0 and 1 until it is measured. SuperpositionThe core principle that allows a qubit to be in multiple states at once. A qubit's state is a weighted combination of |0⟩ and |1⟩.A qubit can be in a state that is 60% |0⟩ and 40% |1⟩. It is not one or the other; it is probabilistically both until a measurement is made. EntanglementA phenomenon where two or more qubits become linked in such a way that...
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Core Syntax & Patterns

Qubit State Vector |ψ⟩ = α|0⟩ + β|1⟩, where |α|² + |β|² = 1 This is the standard way to represent a qubit's state. |ψ⟩ (psi) is the state vector. α and β are complex numbers called 'probability amplitudes'. The probability of measuring the qubit as 0 is |α|², and the probability of measuring it as 1 is |β|². The sum of these probabilities must equal 1 (100%). Hadamard Gate (H) H|0⟩ = (|0⟩ + |1⟩)/√2 H|1⟩ = (|0⟩ - |1⟩)/√2 The Hadamard gate is a fundamental operation used to create superposition. When applied to a qubit in the |0⟩ state, it creates an equal superposition where there's a 50% chance of measuring 0 and a 50% chance of measuring 1. CNOT Gate (Controlled-NOT) Flips the target qubit if and only if the control qubit is |1⟩. This is a two-qu...

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Sample Practice Questions

Challenging
Following the tutorial's worked example, what is the complete sequence of gates required to transform the initial state |00⟩ into the entangled Bell state (1/√2)(|00⟩ + |11⟩)?
A.Apply a CNOT to the first qubit, then a Hadamard to the second qubit.
B.Apply a Hadamard gate to both qubits simultaneously.
C.Apply a CNOT gate where qubit 1 is control and qubit 2 is target, then apply a Hadamard gate to qubit 1.
D.Apply a Hadamard gate to qubit 1, then apply a CNOT gate where qubit 1 is control and qubit 2 is target.
Challenging
Two qubits are in the entangled Bell state (1/√2)(|00⟩ + |11⟩). If you measure the first qubit and the result is 1, what is the state of the second qubit *immediately after* this measurement?
A.The second qubit is guaranteed to be in the state |1⟩.
B.The second qubit is in the superposition state (|0⟩ + |1⟩)/√2.
C.The second qubit is guaranteed to be in the state |0⟩.
D.The second qubit has a 50% chance of being |0⟩ and a 50% chance of being |1⟩.
Challenging
A qubit is prepared in the state |ψ⟩ = (1/2)|0⟩ + (√3/2)|1⟩. If you prepare 10,000 identical copies of this qubit and measure each one, approximately how many times would you expect to measure the state |0⟩?
A.5,000
B.2,500
C.7,500
D.8,660

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