Preparing multi-partite entanglement of photons and matter qubits

We show how to make event-ready multi-partite entanglement between qubits which may be encoded on photons or matter systems. Entangled states of matter systems, which can also act as single photon sources, can be generated using the entangling operation presented in Barrett and Kok (2004 Preprint quant-ph/0408040). We show how to entangle such sources with photon qubits, which may be encoded in the dual-rail, polarization or time-bin degrees of freedom. We subsequently demonstrate how projective measurements of the matter qubits can be used to create entangled states of the photons alone. The state of the matter qubits is inherited by the generated photons. Since the entangling operation can be used to generate cluster states of matter qubits for quantum computing, our procedure enables us to create any (entangled) photonic quantum state that can be written as the outcome of a quantum computer.We show how to make event-ready multi-partite entanglement between qubits which may be encoded on photons or matter systems. Entangled states of matter systems, which can also act as single photon sources, can be generated using the entangling operation presented in Barrett and Kok (2004 Preprint quant-ph/0408040). We show how to entangle such sources with photon qubits, which may be encoded in the dual-rail, polarization or time-bin degrees of freedom. We subsequently demonstrate how projective measurements of the matter qubits can be used to create entangled states of the photons alone. The state of the matter qubits is inherited by the generated photons. Since the entangling operation can be used to generate cluster states of matter qubits for quantum computing, our procedure enables us to create any (entangled) photonic quantum state that can be written as the outcome of a quantum computer.

arXiv:quant-ph/0506164Journal of Optics B Quantum and Semiclassical OpticsJun 30, 20055 citations

Generation of high-dimensional photonic entanglement

Alex E. Jones, Stefano Paesani, Jacob F. F. Bulmer +2 more

Photonics is a sophisticated platform for the development of novel quantum technologies, from quantum processors to distributed quantum communication. Most linear optical architectures focus on encoding qubits into photons using, for example, polarization or a dual-rail approach. However, encoding higher-dimensional systems - qudits - can in principle provide improved information capacity and noise tolerance in communication, and lower error thresholds in fault-tolerant quantum computation. Here we present new schemes for generating high-dimensional photonic entanglement and discuss how to build cluster states for universal high-dimensional quantum computation.Photonics is a sophisticated platform for the development of novel quantum technologies, from quantum processors to distributed quantum communication. Most linear optical architectures focus on encoding qubits into photons using, for example, polarization or a dual-rail approach. However, encoding higher-dimensional systems - qudits - can in principle provide improved information capacity and noise tolerance in communication, and lower error thresholds in fault-tolerant quantum computation. Here we present new schemes for generating high-dimensional photonic entanglement and discuss how to build cluster states for universal high-dimensional quantum computation.

Quantum Nanophotonic Materials, Devices, and SystemsJul 30, 20210 citations

Flexible entangled-state generation in linear optics

Brendan Pankovich, Alex Neville, Angus Kan +3 more

Entangled dual-rail photonic qubit states are important resource states for measurement-based and fusion-based quantum computing. However, their generation is highly challenging due to the probabilistic nature of entangling operations. Here, the authors introduce a formalism using ZX diagrams to design linear optical systems that can generate entangled multiqubit states of dual-rail photonic qubits. This formalism makes it easier to compare methods for creating a desired photonic state and to find the most optimal one.Entangled dual-rail photonic qubit states are important resource states for measurement-based and fusion-based quantum computing. However, their generation is highly challenging due to the probabilistic nature of entangling operations. Here, the authors introduce a formalism using ZX diagrams to design linear optical systems that can generate entangled multiqubit states of dual-rail photonic qubits. This formalism makes it easier to compare methods for creating a desired photonic state and to find the most optimal one.

arXiv:2310.06832Physical Review ASep 4, 202410 citations

Entanglement Swapping as Event-Ready Entanglement Preparation

Pieter Kok, Samuel L. Braunstein

In this contribution the preparation of event-ready entanglement in polarised photons by means of entanglement swapping is studied. This protocol makes use of Gaussian photon-sources. Since the states resulting from this protocol are equivalent to those obtained by mixing two photons in a 50:50 beam splitter, the nature of the emerging entanglement is controversial. Several methods to enhance the fidelity of the outgoing state are studied. It is found that at least quantum non-demolition measurements or a quantum computer of some kind is needed to create event-ready entanglement with entanglement swapping.In this contribution the preparation of event-ready entanglement in polarised photons by means of entanglement swapping is studied. This protocol makes use of Gaussian photon-sources. Since the states resulting from this protocol are equivalent to those obtained by mixing two photons in a 50:50 beam splitter, the nature of the emerging entanglement is controversial. Several methods to enhance the fidelity of the outgoing state are studied. It is found that at least quantum non-demolition measurements or a quantum computer of some kind is needed to create event-ready entanglement with entanglement swapping.

Fortschritte der PhysikMay 1, 20004 citations

Quantum Entanglement between Optical and Microwave Photonic Qubits

Srujan Meesala, David P. Lake, Steven M. Wood +6 more

Entanglement is an extraordinary feature of quantum mechanics. Sources of entangled optical photons were essential to test the foundations of quantum physics through violations of Bell’s inequalities. More recently, entangled many-body states have been realized via strong nonlinear interactions in microwave circuits with superconducting qubits. Here, we demonstrate a chip-scale source of entangled optical and microwave photonic qubits. Our device platform integrates a piezo-optomechanical transducer with a superconducting resonator which is robust under optical illumination. We drive a photon-pair generation process and employ a dual-rail encoding intrinsic to our system to prepare entangled states of microwave and optical photons. We place a lower bound on the fidelity of the entangled state by measuring microwave and optical photons in two orthogonal bases. This entanglement source can directly interface telecom wavelength time-bin qubits and gigahertz frequency superconducting qubits, two well-established platforms for quantum communication and computation, respectively. Published by the American Physical Society 2024Entanglement is an extraordinary feature of quantum mechanics. Sources of entangled optical photons were essential to test the foundations of quantum physics through violations of Bell’s inequalities. More recently, entangled many-body states have been realized via strong nonlinear interactions in microwave circuits with superconducting qubits. Here, we demonstrate a chip-scale source of entangled optical and microwave photonic qubits. Our device platform integrates a piezo-optomechanical transducer with a superconducting resonator which is robust under optical illumination. We drive a photon-pair generation process and employ a dual-rail encoding intrinsic to our system to prepare entangled states of microwave and optical photons. We place a lower bound on the fidelity of the entangled state by measuring microwave and optical photons in two orthogonal bases. This entanglement source can directly interface telecom wavelength time-bin qubits and gigahertz frequency superconducting qubits, two well-established platforms for quantum communication and computation, respectively. Published by the American Physical Society 2024

arXiv:2312.13559Physical Review XSep 30, 202434 citations

Multiphoton entanglement through a Bell-multiport beam splitter

Yuan Liang Lim, Almut Beige

Multiphoton entanglement is an important resource for linear optics quantum computing. Here we show that a wide range of highly entangled multiphoton states, including $W$ -states, can be prepared by interfering single photons inside a Bell multiport beam splitter and using postselection. A successful state preparation is indicated by the collection of one photon per output port. An advantage of the Bell multiport beam splitter is that it redirects the photons without changing their inner degrees of freedom. The described setup can therefore be used to generate polarization, time-bin, and frequency multiphoton entanglement, even when using only a single photon source.Multiphoton entanglement is an important resource for linear optics quantum computing. Here we show that a wide range of highly entangled multiphoton states, including $W$-states, can be prepared by interfering single photons inside a Bell multiport beam splitter and using postselection. A successful state preparation is indicated by the collection of one photon per output port. An advantage of the Bell multiport beam splitter is that it redirects the photons without changing their inner degrees of freedom. The described setup can therefore be used to generate polarization, time-bin, and frequency multiphoton entanglement, even when using only a single photon source.

arXiv:quant-ph/0406047Physical Review AJun 13, 200565 citations

Multiphoton entanglement is an important resource for linear optics quantum computing. Here we show that a wide range of highly entangled multiphoton states, including

W

-states, can be prepared by interfering single photons inside a Bell multiport beam splitter and using postselection. A successful state preparation is indicated by the collection of one photon per output port. An advantage of the Bell multiport beam splitter is that it redirects the photons without changing their inner degrees of freedom. The described setup can therefore be used to generate polarization, time-bin, and frequency multiphoton entanglement, even when using only a single photon source.