Experimentally demonstrating indefinite causal order algorithms to solve the generalized Deutsch's problem

Abstract

Deutsch's algorithm is the first quantum algorithm to show the advantage over the classical algorithm. Here we generalize Deutsch's problem to $n$ functions and propose a new quantum algorithm with indefinite causal order to solve this problem. The new algorithm not only reduces the number of queries to the black-box by half over the classical algorithm, but also significantly reduces the number of required quantum gates over the Deutsch's algorithm. We experimentally demonstrate the algorithm in a stable Sagnac loop interferometer with common path, which overcomes the obstacles of both phase instability and low fidelity of Mach-Zehnder interferometer. The experimental results have shown both an ultra-high and robust success probability $\sim 99.7\%$. Our work opens up a new path towards solving the practical problems with indefinite casual order quantum circuits.

References in corpus (13)

• Experimental Verification of an Indefinite Causal Order
• Towards Quantum Gravity: A Framework for Probabilistic Theories with Non-Fixed Causal Structure
• Sending classical information via three noisy channels in superposition of causal orders
• Experimentally feasible computational advantage from quantum superposition of gate orders
• Noisy quantum metrology with the assistance of indefinite causal order
• Experiments on quantum causality
• Thermal devices powered by generalized measurements with indefinite causal order
• Thermodynamics of quantum switch information capacity activation
• Demonstration of Deutsch's Algorithm on a Stable Linear-Optical Quantum Computer
• Implementing the Deutsch's algorithm with spin-orbital angular momentum of photon without interferometer
• Demonstration of a quantum SWITCH in a Sagnac configuration
• Quantum communication using a quantum switch of quantum switches
• Practical computational advantage from the quantum switch on a generalized family of promise problems

Cited by in corpus (8)

• Experimental Aspects of Indefinite Causal Order in Quantum Mechanics
• Deterministic generation of multi-qubit entangled states among distant parties using indefinite causal order
• Activation of thermal states by coherently controlled thermalization processes
• Mapping indefinite causal order processes to composable quantum protocols in a spacetime
• Expressibility, entangling power and quantum average causal effect for causally indefinite circuits
• Practical implementation of arbitrary nonlocal controlled-unitary gate via indefinite causal order
• Estimation of multivariate traces of states given partial classical information
• Correlations in a quantum switch-based heat engine with measurements: A proof-of-principle demonstration