Final Report Summary - CRYTERION (Cryogenic Traps for Entanglement Research with Ions)
Background:
Table-top quantum science has provided an important playground for the investigation of quantum phenomena. Over the past twenty years this has led to the development of the still-growing fields of cold-ion physics and quantum information science. These provide the instruments and machinery to explore and answer questions from fundamental quantum physics, from solid state and condensed matter physics, and to investigate information science with quantum tools. Entanglement is at the centre of many of the counterintuitive effects seen in quantum mechanics, and at the same time provides a new tool for different forms of quantum information processing, for new methods of (secure) communication, and for improvements of quantum-limited measurements. Using small linear chains of trapped ions the Innsbruck group has previously demonstrated simple quantum algorithms such as deterministic teleportation protocols and entanglement purification. We have also implemented long-lived quantum registers, measurement-controlled gate operations and realised of the world’s first quantum byte (eight quantum bits, or qubits).
Vision:
The vision of the CRYTERION project was to push beyond this: beyond eight ions, beyond simple algorithms, beyond linear chains, and even beyond individual ion traps. The target was to be able to manipulate the quantum state of around fifteen ions, and thereby perform physically interesting quantum simulations. We also planned to entirely redesign the ion trap structure so that instead of being limited to a single chain of ions in a single trap we could have multiple chains, either aligned with each other, or distributed in a two-dimensional trap array. Finally, we wished to consider ways to get the quantum information out of the ion trap by coupling it to some other quantum system, such as light.
Accomplishments:
In the first instance we have advanced what we had in existing systems – those using a few ions – to fully understand and characterise the quantum tools at hand, so that they can then be taken forward. We have moved the state of the art from being able to entangle up to eight qubits: through the work carried out in this project we have been able to entangle fourteen qubits, and even carry out extended quantum simulations on fifteen qubits. Operations on so many qubits are, however, tremendously fragile. With this in mind, we have characterised what it is that destroys the quantum nature of the states, and implemented new ways to protect the ions from such disturbances.
On a second front, we have looked even further ahead, to develop technologies which will provide a platform for the future of scalable quantum information processing. We have developed new kinds of traps, and new ways of controlling those traps, so that ions can be manipulated in configurations which were previously unattainable. We have been able to trap chains of ions, aligned in multiple traps, and use the ions’ motion to engineer quantum interactions between the different traps. We have also created architectures capable of holding ions in a two-dimensional array, with a view to controllably selecting which sites should interact. Further work - to move these new traps beyond simple demonstration experiments - will ultimately have applications for simulating numerous systems, from superconductivity to biologically important molecules.
Finally, we have looked beyond the trapped ions themselves, to investigate how ions interact with light. At a technological level we have worked on ways to efficiently couple different ion traps via photons using optical fibres. At the most fundamental level, we have also investigated the interaction of single photons with single atomic ions. This has allowed us to take standard optics experiments – such as the reflection of light at a mirror – and investigate what happens if the “mirror” consists of only a single atom.
Taken together, the CRYTERION project has provided a suite of experiments pushing forward our understanding of entanglement. We have investigated entanglement and decoherence both at the level of fundamental physics, and in applied experiments, where the control thereby afforded paves the way to concrete uses. We have also worked to build future technologies which consider not just the limits on a state-of-the-art quantum system today, but prepare for entanglement studies in quantum computers of the future.
Table-top quantum science has provided an important playground for the investigation of quantum phenomena. Over the past twenty years this has led to the development of the still-growing fields of cold-ion physics and quantum information science. These provide the instruments and machinery to explore and answer questions from fundamental quantum physics, from solid state and condensed matter physics, and to investigate information science with quantum tools. Entanglement is at the centre of many of the counterintuitive effects seen in quantum mechanics, and at the same time provides a new tool for different forms of quantum information processing, for new methods of (secure) communication, and for improvements of quantum-limited measurements. Using small linear chains of trapped ions the Innsbruck group has previously demonstrated simple quantum algorithms such as deterministic teleportation protocols and entanglement purification. We have also implemented long-lived quantum registers, measurement-controlled gate operations and realised of the world’s first quantum byte (eight quantum bits, or qubits).
Vision:
The vision of the CRYTERION project was to push beyond this: beyond eight ions, beyond simple algorithms, beyond linear chains, and even beyond individual ion traps. The target was to be able to manipulate the quantum state of around fifteen ions, and thereby perform physically interesting quantum simulations. We also planned to entirely redesign the ion trap structure so that instead of being limited to a single chain of ions in a single trap we could have multiple chains, either aligned with each other, or distributed in a two-dimensional trap array. Finally, we wished to consider ways to get the quantum information out of the ion trap by coupling it to some other quantum system, such as light.
Accomplishments:
In the first instance we have advanced what we had in existing systems – those using a few ions – to fully understand and characterise the quantum tools at hand, so that they can then be taken forward. We have moved the state of the art from being able to entangle up to eight qubits: through the work carried out in this project we have been able to entangle fourteen qubits, and even carry out extended quantum simulations on fifteen qubits. Operations on so many qubits are, however, tremendously fragile. With this in mind, we have characterised what it is that destroys the quantum nature of the states, and implemented new ways to protect the ions from such disturbances.
On a second front, we have looked even further ahead, to develop technologies which will provide a platform for the future of scalable quantum information processing. We have developed new kinds of traps, and new ways of controlling those traps, so that ions can be manipulated in configurations which were previously unattainable. We have been able to trap chains of ions, aligned in multiple traps, and use the ions’ motion to engineer quantum interactions between the different traps. We have also created architectures capable of holding ions in a two-dimensional array, with a view to controllably selecting which sites should interact. Further work - to move these new traps beyond simple demonstration experiments - will ultimately have applications for simulating numerous systems, from superconductivity to biologically important molecules.
Finally, we have looked beyond the trapped ions themselves, to investigate how ions interact with light. At a technological level we have worked on ways to efficiently couple different ion traps via photons using optical fibres. At the most fundamental level, we have also investigated the interaction of single photons with single atomic ions. This has allowed us to take standard optics experiments – such as the reflection of light at a mirror – and investigate what happens if the “mirror” consists of only a single atom.
Taken together, the CRYTERION project has provided a suite of experiments pushing forward our understanding of entanglement. We have investigated entanglement and decoherence both at the level of fundamental physics, and in applied experiments, where the control thereby afforded paves the way to concrete uses. We have also worked to build future technologies which consider not just the limits on a state-of-the-art quantum system today, but prepare for entanglement studies in quantum computers of the future.