Coupling trapped ions via transmission lines for quantum computing

Today computers are indispensable even in our daily life. Each year engineers create smaller and more powerful computers. With the current rate of miniaturization in about 20 years bits will consist out of single atoms. For such small objects like single atoms, however, our usual intuition fails and we enter the realm of quantum mechanics. Is it still possible to build a computer based on these strange, new quantum rules? Intriguingly, such a quantum computer cannot only be build but can also solve certain problems more efficiently than normal computers. Quantum bits, or short "qubits", are the elementary carriers of quantum information in such a device. A quantum computer consisting of only forty qubits can already simulate quantum mechanical systems which are intractable with current computers. For the computation, the qubits must be initialized, manipulated and read-out with very high fidelities. This is a formidable task for quantum systems. However, using trapped ions these tasks have already been realized with up to eight qubits. The present proposal seeks to increase the number of qubits in ion trap quantum computers even further by coupling two or more ion traps to each other using wires. Thus the quantum motion of a trapped ion induces a current in the wires which in turn then acts on the motion of the ions trapped in a different quantum computer. Thus the qubits contents can be transmitted over superconducting wires, which preserve the quantum information. This inter-trap coupling may not only be used to realize a scalable quantum computer, but also for probing and manipulating the quantum properties of the wires themselves. For instance, cooling the ions continuously, the ions will extract heat from the wires. Thus the thermal motion of the electrons in the wires can be brought almost to rest. With such experiments the decoherence properties of charge transport in wires can be investigated in a completely new regime. This work opens new ways to interconnect quantum computers and thus facilitates the building of useful quantum computer. Such quantum computers might be used to simulate and model quantum mechanical many body systems of unequalled accuracy. As the ions can also be read out with nearly 100 % quantum efficiency, a single ion can be used an almost perfect quantum amplifier. For instance currents as small as a billionth of a billionth Ampere can be detected with the proposed method.

Today computers are indispensable even in our daily life. Each year engineers create smaller and more powerful computers. With the current rate of miniaturization in about 20 years bits will consist out of single atoms. For such small objects like single atoms, however, our usual intuition fails and we enter the realm of quantum mechanics. Is it still possible to build a computer based on these strange, new quantum rules? Intriguingly, such a quantum computer cannot only be build but can also solve certain problems more efficiently than normal computers. Quantum bits, or short "qubits", are the elementary carriers of quantum information in such a device. A quantum computer consisting of only forty qubits can already simulate quantum mechanical systems which are intractable with current computers. For the computation, the qubits must be initialized, manipulated and read-out with very high fidelities. This is a formidable task for quantum systems. However, using trapped ions these tasks have already been realized with up to eight qubits. The present proposal seeks to increase the number of qubits in ion trap quantum computers even further by coupling two or more ion traps to each other using wires. Thus the quantum motion of a trapped ion induces a current in the wires which in turn then acts on the motion of the ions trapped in a different quantum computer. Thus the qubits contents can be transmitted over superconducting wires, which preserve the quantum information. This inter-trap coupling may not only be used to realize a scalable quantum computer, but also for probing and manipulating the quantum properties of the wires themselves. For instance, cooling the ions continuously, the ions will extract heat from the wires. Thus the thermal motion of the electrons in the wires can be brought almost to rest. With such experiments the decoherence properties of charge transport in wires can be investigated in a completely new regime. This work opens new ways to interconnect quantum computers and thus facilitates the building of useful quantum computer. Such quantum computers might be used to simulate and model quantum mechanical many body systems of unequalled accuracy. As the ions can also be read out with nearly 100 % quantum efficiency, a single ion can be used an almost perfect quantum amplifier. For instance currents as small as a billionth of a billionth Ampere can be detected with the proposed method.