ORCID Profile
0000-0002-4964-817X
Current Organisation
University of Vienna
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Publisher: Springer Science and Business Media LLC
Date: 07-08-2015
DOI: 10.1038/NCOMMS8913
Abstract: Quantum computers achieve a speed-up by placing quantum bits (qubits) in superpositions of different states. However, it has recently been appreciated that quantum mechanics also allows one to ‘superimpose different operations’. Furthermore, it has been shown that using a qubit to coherently control the gate order allows one to accomplish a task—determining if two gates commute or anti-commute—with fewer gate uses than any known quantum algorithm. Here we experimentally demonstrate this advantage, in a photonic context, using a second qubit to control the order in which two gates are applied to a first qubit. We create the required superposition of gate orders by using additional degrees of freedom of the photons encoding our qubits. The new resource we exploit can be interpreted as a superposition of causal orders, and could allow quantum algorithms to be implemented with an efficiency unlikely to be achieved on a fixed-gate-order quantum computer.
Publisher: Springer Science and Business Media LLC
Date: 05-08-2012
DOI: 10.1038/NPHYS2377
Publisher: American Physical Society (APS)
Date: 10-10-2021
Publisher: American Physical Society (APS)
Date: 27-10-2015
Publisher: Springer Science and Business Media LLC
Date: 19-08-2014
DOI: 10.1038/SREP06115
Abstract: Large-scale quantum computers will require the ability to apply long sequences of entangling gates to many qubits. In a photonic architecture, where single-qubit gates can be performed easily and precisely, the application of consecutive two-qubit entangling gates has been a significant obstacle. Here, we demonstrate a two-qubit photonic quantum processor that implements two consecutive CNOT gates on the same pair of polarisation-encoded qubits. To demonstrate the flexibility of our system, we implement various instances of the quantum algorithm for solving of systems of linear equations.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 08-2003
Abstract: We demonstrate the distribution of quantum entanglement via optical free-space links to independent receivers separated by 600 m, with no line of sight between each other. A Bell inequality between those receivers is violated by more than four standard deviations, confirming the quality of the entanglement. This outdoor experiment represents a step toward satellite-based distributed quantum entanglement.
No related grants have been discovered for Philip Walther.