Self-Assessment Quiz: Dynamic Circuits

Twenty questions. The teleportation misconceptions (11–14) are the ones worth getting right, because you will be asked about them. Aim for 16 or more.

Question 1

A dynamic circuit is one that: - A. runs faster - B. measures mid-circuit and applies gates conditioned on the result, within one execution - C. uses fewer qubits - D. changes its qubit count at runtime

Question 2

Dynamic circuits change: - A. what is computable - B. what is practical — qubit reuse, error correction, protocols like teleportation - C. nothing - D. the number of shots required

Question 3

The modern syntax for classical feedforward is: - A. qc.x(1).c_if(qc.clbits[0], 1) - B. with qc.if_test((qc.clbits[0], 1)): qc.x(1) - C. qc.conditional_x(1, 0) - D. qc.if(0).x(1)

Question 4

c_if was removed because: - A. it was slow - B. it could only condition a single gate on a register equality - C. it did not work - D. it was renamed

Question 5

In teleportation, Alice performs a Bell measurement by applying: - A. h then cx - B. cx then h, then measuring both - C. two Hadamards - D. a Toffoli

Question 6

Bob's correction depends on: - A. the state being teleported - B. Alice's two classical measurement bits - C. the distance between them - D. nothing; no correction is needed

Question 7

How many distinct corrections are possible? - A. 2 - B. 3 - C. 4 - D. 8

Question 8

Alice's two measurement outcomes occur with probabilities: - A. depending on the teleported state - B. roughly 25% each, independent of the state - C. always 00 - D. 50/50 between 00 and 11

Question 9

Verifying teleportation by comparing the $Z$ distribution alone is: - A. sufficient proof - B. nearly worthless — a circuit that merely prepared the right probabilities would pass - C. impossible - D. the standard practice and correct

Question 10

Verifying in all three Bloch bases is equivalent to: - A. nothing extra - B. single-qubit state tomography, which completely determines a pure state - C. measuring twice as long - D. an entanglement witness

Question 11

Teleportation does not violate no-cloning because: - A. the state is copied but the copy is imperfect - B. Alice's measurement destroys the original — two copies never coexist - C. no-cloning does not apply to qubits - D. it does violate it

Question 12

Teleportation does not transmit information faster than light because: - A. the entanglement is slow - B. Bob's qubit is one of four states until Alice's two classical bits arrive, and those travel classically - C. the qubits decohere - D. it does transmit faster than light

Question 13

What physically travels from Alice to Bob? - A. the qubit - B. two classical bits - C. energy - D. nothing at all

Question 14

The exact exchange rate of teleportation is: - A. 1 qubit → 1 qubit - B. 1 entangled pair + 2 classical bits → 1 transmitted qubit state - C. 2 qubits → 1 classical bit - D. 1 classical bit → 1 qubit

Question 15

Superdense coding sends: - A. 1 classical bit using 2 qubits - B. 2 classical bits using 1 transmitted qubit plus a pre-shared entangled pair - C. 4 classical bits using 1 qubit - D. an unlimited number of bits

Question 16

In the measured results, Alice sending 01 produced Bob measuring '10' because: - A. the protocol is wrong - B. little-endian ordering interacting with which bit drives the X gate - C. of noise - D. Bob decoded incorrectly

Question 17

That bug would have been hidden by testing only: - A. 01 and 10 - B. 00 and 11 — both palindromes - C. all four messages - D. a single message

Question 18

reset enables qubit reuse by converting: - A. depth into width - B. a width constraint into a depth constraint - C. errors into corrections - D. classical bits into qubits

Question 19

Qubit reuse is generally not useful for VQE because: - A. reset is unsupported - B. the ansatz keeps every qubit entangled throughout — there is nothing free to reuse - C. VQE uses too few qubits - D. it changes the answer

Question 20

The largest cost of a dynamic circuit is: - A. the extra gates - B. the measure-decide-act latency, during which other qubits sit idle — invisible to depth() - C. the classical bits - D. transpilation time

Answers

# Answer Why
1 B Within one execution, state still live. §9.1
2 B Not computability — practicality. §9.2
3 B A context manager, with optional else. §9.1
4 B Which is why QASM 2 could not express dynamic circuits. §9.1 Version Note
5 B Chapter 4 §4.5's entangler run backward. §9.3
6 B Two bits, four corrections. §9.3
7 C none, $X$, $Z$, $X$ then $Z$. §9.3
8 B Measured ~2000 each of 8192. §9.3
9 B Chapter 4 Case Study 2's discipline. §9.3
10 B Three Bloch components determine a pure state. §9.3
11 B The original is destroyed. §9.3 pitfall
12 B The classical message carries the information. §9.3 pitfall
13 B Only two classical bits. §9.3 pitfall
14 B Worth memorizing verbatim. §9.3
15 B The pair is distributed in advance. §9.4
16 B Two reversals interacting. §9.4 pitfall
17 B Palindromes hide ordering errors. §9.4, Ch. 5 §5.3
18 B Often a good trade — but see 19. §9.5
19 B That is what entangling layers are for. §9.5, §9.7 checkpoint
20 B Gates are tens of ns; the round trip is hundreds to thousands. §9.7

Topic Map

Questions Topic Section If you missed these
1–4 Feedforward syntax §9.1, §9.2 Do Exercise 9.6
5–8 Teleportation mechanics §9.3 Build it; the correction table is the core
9, 10 Verification §9.3 Do Exercise 9.7. One basis proves nothing
11–14 The misconceptions §9.3 pitfall Be able to answer these cold. You will be asked
15–17 Superdense coding §9.4 Exercise 9.9; the ordering trap is instructive
18, 19 Reuse §9.5 Exercise 9.10, then the checkpoint's negative result
20 The hidden cost §9.7 The question to ask is "how long do qubits sit idle?"

Score 16+: go to Chapter 10.

Score 12–15: if you missed any of 11–14, fix that first. Those four are the questions a non-specialist will actually ask you, and getting them right is a large part of being useful.

Score under 12: the protocol mechanics are reference. The two things to carry forward: verify in more than one basis, and the classical bits are what carry the information.