Demonstration of Blind Quantum Computing

Abstract

Quantum computers, besides offering substantial computational speedups, are also expected to preserve the privacy of a computation. We present an experimental demonstration of blind quantum computing in which the input, computation, and output all remain unknown to the computer. We exploit the conceptual framework of measurement-based quantum computation that enables a client to delegate a computation to a quantum server. Various blind delegated computations, including one- and two-qubit gates and the Deutsch and Grover quantum algorithms, are demonstrated. The client only needs to be able to prepare and transmit individual photonic qubits. Our demonstration is crucial for unconditionally secure quantum cloud computing and might become a key ingredient for real-life applications, especially when considering the challenges of making powerful quantum computers widely available.

Quantum computing on encrypted data

“…While some of these schemes, in principle, can be used to accomplish similar outcomes as our protocol, they can lead to very different client-server relationships in practice. For example, a recent experiment used the measurement-based model of quantum computing to demonstrate the complementary problem of hiding from a server the circuit that is to be performed 7,8 . This method, known as blind quantum computing, can be extended to compute on encrypted data, but would require more than eight times as many auxiliary qubits and significantly more rounds of classical communication.…”

“…The overhead in quantum resources required to compute on encrypted quantum data is so low (only one auxiliary qubit per non-Clifford gate) that it will be straightforward for future quantum servers to incorporate our protocol in their design, dramatically enhancing the security of client-server quantum computing; our protocol has even less overhead than the best classical fully homomorphic encryption scheme, and provides information-theoretic (as opposed to just computational) security. This method for computing on encrypted quantum data, combined with the techniques developed for quantum circuit hiding 7,8 , form a complete security system that will enable secure distributed quantum computing to take place, ensuring the privacy and security of future quantum networks.…”

Garbled Quantum Computation

“…Among them is the universal blind quantum computation (UBQC) protocol of [3], which is developed based on the measurement-based quantum computation model (MBQC) [7] that appears as the most promising physical implementation for a networked architecture [8]. In the UBQC framework, the only quantum requirement for the client is the offline creation of random single qubit states, which is a currently available technology and has been demonstrated experimentally [9].…”

Quantum Walks with Encrypted Data

“…Universal classical homomorphic encryption was only first discovered in 2009 [6] and subsequently simplified [7]. Closely related is blind computing, where Alice possesses both the data and the algorithm, and Bob owns the computer [8][9][10], as is the quantum private queries protocol [11], which is used to query a database while keeping the query secret.In this paper we describe a technique for solving the above problem, and hence achieving a limited quantum homomorphic encryption using the Boson sampling and multi-walker quantum walk models for quantum computation.The Boson sampling model -A first protocol for universal LOQC was introduced by Knill, Laflamme & Milburn (KLM) [4]. While universal for quantum computation, their protocol is extremely demanding, requiring fast-feedforward and quantum memory, which are technologically challenging and well beyond the capabilities of present-day experiments.…”

“…Universal classical homomorphic encryption was only first discovered in 2009 [6] and subsequently simplified [7]. Closely related is blind computing, where Alice possesses both the data and the algorithm, and Bob owns the computer [8][9][10], as is the quantum private queries protocol [11], which is used to query a database while keeping the query secret.…”