251 research outputs found
Verification of Many-Qubit States
Verification is a task to check whether a given quantum state is close to an
ideal state or not. In this paper, we show that a variety of many-qubit quantum
states can be verified with only sequential single-qubit measurements of Pauli
operators. First, we introduce a protocol for verifying ground states of
Hamiltonians. We next explain how to verify quantum states generated by a
certain class of quantum circuits. We finally propose an adaptive test of
stabilizers that enables the verification of all polynomial-time-generated
hypergraph states, which include output states of the
Bremner-Montanaro-Shepherd-type instantaneous quantum polynomial time (IQP)
circuits. Importantly, we do not make any assumption that the identically and
independently distributed copies of the same states are given: Our protocols
work even if some highly complicated entanglement is created among copies in
any artificial way. As applications, we consider the verification of the
quantum computational supremacy demonstration with IQP models, and verifiable
blind quantum computing.Comment: 15 pages, 3 figures, published versio
Merlin-Arthur with efficient quantum Merlin and quantum supremacy for the second level of the Fourier hierarchy
We introduce a simple sub-universal quantum computing model, which we call
the Hadamard-classical circuit with one-qubit (HC1Q) model. It consists of a
classical reversible circuit sandwiched by two layers of Hadamard gates, and
therefore it is in the second level of the Fourier hierarchy. We show that
output probability distributions of the HC1Q model cannot be classically
efficiently sampled within a multiplicative error unless the polynomial-time
hierarchy collapses to the second level. The proof technique is different from
those used for previous sub-universal models, such as IQP, Boson Sampling, and
DQC1, and therefore the technique itself might be useful for finding other
sub-universal models that are hard to classically simulate. We also study the
classical verification of quantum computing in the second level of the Fourier
hierarchy. To this end, we define a promise problem, which we call the
probability distribution distinguishability with maximum norm (PDD-Max). It is
a promise problem to decide whether output probability distributions of two
quantum circuits are far apart or close. We show that PDD-Max is BQP-complete,
but if the two circuits are restricted to some types in the second level of the
Fourier hierarchy, such as the HC1Q model or the IQP model, PDD-Max has a
Merlin-Arthur system with quantum polynomial-time Merlin and classical
probabilistic polynomial-time Arthur.Comment: 30 pages, 4 figure
Quantum computational universality of hypergraph states with Pauli-X and Z basis measurements
Measurement-based quantum computing is one of the most promising quantum
computing models. Although various universal resource states have been proposed
so far, it was open whether only two Pauli bases are enough for both of
universal measurement-based quantum computing and its verification. In this
paper, we construct a universal hypergraph state that only requires and
-basis measurements for universal measurement-based quantum computing. We
also show that universal measurement-based quantum computing on our hypergraph
state can be verified in polynomial time using only and -basis
measurements. Furthermore, in order to demonstrate an advantage of our
hypergraph state, we construct a verifiable blind quantum computing protocol
that requires only and -basis measurements for the client.Comment: 12 pages, 8 figures, 1 table, close to published versio
Sumcheck-based delegation of quantum computing to rational server
Delegated quantum computing enables a client with a weak computational power
to delegate quantum computing to a remote quantum server in such a way that the
integrity of the server is efficiently verified by the client. Recently, a new
model of delegated quantum computing has been proposed, namely, rational
delegated quantum computing. In this model, after the client interacts with the
server, the client pays a reward to the server. The rational server sends
messages that maximize the expected value of the reward. It is known that the
classical client can delegate universal quantum computing to the rational
quantum server in one round. In this paper, we propose novel one-round rational
delegated quantum computing protocols by generalizing the classical rational
sumcheck protocol. The construction of the previous rational protocols depends
on gate sets, while our sumcheck technique can be easily realized with any
local gate set. Furthermore, as with the previous protocols, our reward
function satisfies natural requirements. We also discuss the reward gap. Simply
speaking, the reward gap is a minimum loss on the expected value of the
server's reward incurred by the server's behavior that makes the client accept
an incorrect answer. Although our sumcheck-based protocols have only
exponentially small reward gaps as with the previous protocols, we show that a
constant reward gap can be achieved if two non-communicating but entangled
rational servers are allowed. We also discuss that a single rational server is
sufficient under the (widely-believed) assumption that the learning-with-errors
problem is hard for polynomial-time quantum computing. Apart from these
results, we show, under a certain condition, the equivalence between
and delegated quantum computing protocols. Based on this
equivalence, we give a reward-gap amplification method.Comment: 28 pages, 1 figure, Because of the character limitation, the abstract
was shortened compared with the PDF fil
Interactive Proofs with Polynomial-Time Quantum Prover for Computing the Order of Solvable Groups
In this paper we consider what can be computed by a user interacting with a potentially malicious server, when the server performs polynomial-time quantum computation but the user can only perform polynomial-time classical (i.e., non-quantum) computation. Understanding the computational power of this model, which corresponds to polynomial-time quantum computation that can be efficiently verified classically, is a well-known open problem in quantum computing. Our result shows that computing the order of a solvable group, which is one of the most general problems for which quantum computing exhibits an exponential speed-up with respect to classical computing, can be realized in this model
Divide-and-conquer verification method for noisy intermediate-scale quantum computation
Several noisy intermediate-scale quantum computations can be regarded as
logarithmic-depth quantum circuits on a sparse quantum computing chip, where
two-qubit gates can be directly applied on only some pairs of qubits. In this
paper, we propose a method to efficiently verify such noisy intermediate-scale
quantum computation. To this end, we first characterize small-scale quantum
operations with respect to the diamond norm. Then by using these characterized
quantum operations, we estimate the fidelity between an actual -qubit output state obtained from the noisy intermediate-scale quantum computation and the
ideal output state (i.e., the target state) . Although the
direct fidelity estimation method requires copies of on average, our method requires only copies even in the
worst case, where is the denseness of . For
logarithmic-depth quantum circuits on a sparse chip, is at most
, and thus is a polynomial in . By using the IBM
Manila 5-qubit chip, we also perform a proof-of-principle experiment to observe
the practical performance of our method.Comment: 17 pages, 7 figures, v3: Added a proof-of-principle experiment (Sec.
IV) and improved Sec. V, Accepted for publication in Quantu
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