Controlled-Z Gate

Description: Test your knowledge on Controlled-Z Gate, a fundamental quantum logic gate used in quantum computing.
Number of Questions: 15
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Tags: quantum computing quantum logic gates controlled-z gate
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What is the purpose of a Controlled-Z Gate in quantum computing?

  1. To perform a controlled phase shift on a qubit.

  2. To entangle two qubits.

  3. To measure the state of a qubit.

  4. To create a superposition of states.


Correct Option: A
Explanation:

The Controlled-Z Gate is used to perform a controlled phase shift on a target qubit, where the phase shift is dependent on the state of a control qubit.

What is the matrix representation of the Controlled-Z Gate?

  1. $$[\begin{bmatrix} 1 & 0 & 0 & 0 \ 0 & 1 & 0 & 0 \ 0 & 0 & 1 & 0 \ 0 & 0 & 0 & -1 ])$$

  2. $$[\begin{bmatrix} 1 & 0 & 0 & 0 \ 0 & 1 & 0 & 0 \ 0 & 0 & -1 & 0 \ 0 & 0 & 0 & 1 ])$$

  3. $$[\begin{bmatrix} 1 & 0 & 0 & 0 \ 0 & -1 & 0 & 0 \ 0 & 0 & 1 & 0 \ 0 & 0 & 0 & 1 ])$$

  4. $$[\begin{bmatrix} 1 & 0 & 0 & 0 \ 0 & -1 & 0 & 0 \ 0 & 0 & -1 & 0 \ 0 & 0 & 0 & 1 ])$$


Correct Option: A
Explanation:

The matrix representation of the Controlled-Z Gate is a 4x4 unitary matrix that applies a phase shift of -1 to the target qubit when the control qubit is in the state |1⟩.

How does the Controlled-Z Gate affect the state of a qubit?

  1. It flips the qubit's state.

  2. It rotates the qubit's state around the Bloch sphere.

  3. It adds a phase shift to the qubit's state.

  4. It measures the qubit's state.


Correct Option: C
Explanation:

The Controlled-Z Gate adds a phase shift of -1 to the target qubit's state when the control qubit is in the state |1⟩.

What is the inverse of the Controlled-Z Gate?

  1. The Controlled-NOT Gate.

  2. The Hadamard Gate.

  3. The Phase Gate.

  4. The Toffoli Gate.


Correct Option: A
Explanation:

The inverse of the Controlled-Z Gate is the Controlled-NOT Gate, which flips the target qubit's state when the control qubit is in the state |1⟩.

What is the Controlled-Z Gate used for in quantum algorithms?

  1. To create entanglement between qubits.

  2. To implement quantum teleportation.

  3. To perform quantum error correction.

  4. All of the above.


Correct Option: D
Explanation:

The Controlled-Z Gate is used in a variety of quantum algorithms, including those for creating entanglement, implementing quantum teleportation, and performing quantum error correction.

How is the Controlled-Z Gate implemented in physical quantum systems?

  1. Using superconducting qubits.

  2. Using trapped ions.

  3. Using photonic qubits.

  4. Using all of the above.


Correct Option: D
Explanation:

The Controlled-Z Gate can be implemented in various physical quantum systems, including superconducting qubits, trapped ions, and photonic qubits.

What is the time complexity of the Controlled-Z Gate?

  1. O(1).

  2. O(log n).

  3. O(n).

  4. O(n^2).


Correct Option: A
Explanation:

The Controlled-Z Gate is a single-qubit gate, and its time complexity is O(1), meaning it takes a constant amount of time to perform.

What is the Controlled-Z Gate's role in quantum error correction?

  1. To detect errors in quantum states.

  2. To correct errors in quantum states.

  3. Both of the above.

  4. None of the above.


Correct Option: C
Explanation:

The Controlled-Z Gate is used in quantum error correction to both detect and correct errors in quantum states.

How does the Controlled-Z Gate relate to the CNOT Gate?

  1. The Controlled-Z Gate is a generalization of the CNOT Gate.

  2. The CNOT Gate is a generalization of the Controlled-Z Gate.

  3. The Controlled-Z Gate and the CNOT Gate are unrelated.

  4. None of the above.


Correct Option: A
Explanation:

The Controlled-Z Gate is a generalization of the CNOT Gate, in the sense that the CNOT Gate can be implemented using the Controlled-Z Gate and a Hadamard Gate.

What is the Controlled-Z Gate's role in quantum teleportation?

  1. To entangle two qubits.

  2. To transfer quantum information from one qubit to another.

  3. Both of the above.

  4. None of the above.


Correct Option: C
Explanation:

The Controlled-Z Gate is used in quantum teleportation to both entangle two qubits and transfer quantum information from one qubit to another.

How does the Controlled-Z Gate contribute to the power of quantum computing?

  1. It enables the creation of entangled states.

  2. It allows for the manipulation of quantum information.

  3. It helps in performing quantum error correction.

  4. All of the above.


Correct Option: D
Explanation:

The Controlled-Z Gate contributes to the power of quantum computing by enabling the creation of entangled states, allowing for the manipulation of quantum information, and helping in performing quantum error correction.

What are some potential applications of the Controlled-Z Gate in quantum computing?

  1. Quantum cryptography.

  2. Quantum simulation.

  3. Quantum machine learning.

  4. All of the above.


Correct Option: D
Explanation:

The Controlled-Z Gate has potential applications in quantum cryptography, quantum simulation, quantum machine learning, and other areas of quantum computing.

How does the Controlled-Z Gate compare to other controlled quantum gates?

  1. It is more powerful than other controlled gates.

  2. It is less powerful than other controlled gates.

  3. It is equally powerful as other controlled gates.

  4. None of the above.


Correct Option: C
Explanation:

The Controlled-Z Gate is equally powerful as other controlled quantum gates, in the sense that any controlled quantum gate can be implemented using the Controlled-Z Gate and other basic quantum gates.

What is the relationship between the Controlled-Z Gate and the Toffoli Gate?

  1. The Toffoli Gate is a generalization of the Controlled-Z Gate.

  2. The Controlled-Z Gate is a generalization of the Toffoli Gate.

  3. The Toffoli Gate and the Controlled-Z Gate are unrelated.

  4. None of the above.


Correct Option: A
Explanation:

The Toffoli Gate is a generalization of the Controlled-Z Gate, in the sense that the Controlled-Z Gate can be implemented using the Toffoli Gate and a Hadamard Gate.

How does the Controlled-Z Gate contribute to the development of quantum algorithms?

  1. It enables the design of more efficient quantum algorithms.

  2. It allows for the implementation of quantum algorithms on physical quantum systems.

  3. Both of the above.

  4. None of the above.


Correct Option: C
Explanation:

The Controlled-Z Gate contributes to the development of quantum algorithms by enabling the design of more efficient quantum algorithms and allowing for the implementation of quantum algorithms on physical quantum systems.

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