Decoherence in Superconducting Quantum Bits by Phonon Radiation

Ioffe, L. B.; Geshkenbeǐn, V. B.; Helm, Ch.; Blatter, G.

doi:10.1103/physrevlett.93.057001

Cited by 54 publications

(54 citation statements)

References 21 publications

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“…The density of TLS was found to be approximately the same as for AlO x barriers. In this qubit we measured a short energy decay time T 1 ∼ 10 ns, a value compatible with loss from phonon radiation due to AlN being piezoelectric [16].…”

Section: Tls In Josephson Junctionsmentioning

confidence: 97%

Superconducting phase qubits

Martinis

2009

Quantum Inf Process

192

197

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Experimental progress is reviewed for superconducting phase qubit research at the University of California, Santa Barbara. The phase qubit has a potential advantage of scalability, based on the low impedance of the device and the ability to microfabricate complex "quantum integrated circuits". Single and coupled qubit experiments, including qubits coupled to resonators, are reviewed along with a discussion of the strategy leading to these experiments. All currently known sources of qubit decoherence are summarized, including energy decay (T 1 ), dephasing (T 2 ), and measurement errors. A detailed description is given for our fabrication process and control electronics, which is directly scalable. With the demonstration of the basic operations needed for quantum computation, more complex algorithms are now within reach.

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Section: Tls In Josephson Junctionsmentioning

confidence: 97%

Superconducting phase qubits

Martinis

2009

Quantum Inf Process

192

197

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“…In addition, since any coupling of qubits to other degrees of freedom can lead to decoherence, it is crucial to understand and control the interaction qubits might have to their mechanical environments 19 .…”

mentioning

confidence: 99%

Quantum acoustics with superconducting qubits

Chu

Kharel

Renninger

et al. 2017

Science

393

325

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The ability to engineer and manipulate different varieties of quantum mechanical objects allows us to take advantage of their unique properties and create useful hybrid technologies 1 .Thus far, complex quantum states and exquisite quantum control have been demonstrated in systems ranging from trapped ions 2, 3 and solid state qubits 4,5 to superconducting microwave resonators 6,7 . Recently, there have been many efforts 8,9 to extend these demonstrations to the motion of complex, macroscopic objects. These mechanical objects have important practical applications in the fields of quantum information and metrology as quantum memories or transducers for measuring and connecting different types of quantum systems. In pursuit of such macroscopic quantum phenomena, mechanical oscillators have been interfaced with quantum devices such as optical cavities and superconducting circuits [10][11][12] . In particular, there have been a few experiments that couple motion to nonlinear quantum objects [13][14][15] such as superconducting qubits. Importantly, this opens up the possibility of creating, storing, and manipulating non-Gaussian quantum states in mechanical degrees of freedom. However, before sophisticated quantum control of mechanical motion can be achieved, we must overcome the challenge of realizing systems with long coherence times while maintaining a 1 arXiv:1703.00342v1 [quant-ph] 1 Mar 2017 sufficient interaction strength. These systems should be implemented in a simple and robust manner that allows for increasing complexity and scalability in the future. Here we experimentally demonstrate a high frequency bulk acoustic wave resonator that is strongly coupled to a superconducting qubit using piezoelectric transduction. In contrast to previous experiments with qubit-mechanical systems [13][14][15] , our device requires only simple fabrication methods, extends coherence times to many microseconds, and provides controllable access to a multitude of phonon modes. We use this system to demonstrate basic quantum operations on the coupled qubit-phonon system. Straightforward improvements to the current device will allow for advanced protocols analogous to what has been shown in optical and microwave resonators, resulting in a novel resource for implementing hybrid quantum technologies.Measuring and controlling the motion of massive objects in the quantum regime is of great interest for both technological applications and for furthering our understanding of quantum mechanics in complex systems. In some respects, the physics of phonons inside a crystal is similar to that of photons inside an electromagnetic resonator, which are routinely treated as quantum mechanical objects. However, such mechanical excitations involve the collective motion of a large number of atoms in the complex environment of a macroscopic object. Nevertheless, there has only been one demonstration of a nonlinear electromechanical system in the strong coupling limit 13 . The outstanding question is how to simultaneously achieve coherences 3 and c...

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“…However, in order to realize such an instability, the energy gain should be linear in the spontaneously generated flux; since our device exhibits only a quadratic dependence on flux, cf. (32), this type of instability is absent.…”

Section: Discussionmentioning

confidence: 99%

“…At the same time, the quadratic dependence on bias allows for a manipulation via ac-fields rather than the usual dc-bias, hence the most dangerous low-frequency part of the noise spectrum can be blocked from the qubit via appropriate filters. ii) The degenerate ground state allows to avoid the appearance of phonon radiation during idle time 32 : Assume a qubit with states |0 and |1 residing at different energies E 0 = E 1 . A superposition state |Ψ (t) = [exp(−iE 0 t/ )|0 +β exp(−iE 1 t/ )|1 ]/ 1 + |β| 2 will induce voltage oscillations V = φ/2e ∝ (E 1 − E 0 )/2e across the Josephson junction which couple to the underlying lattice via the piezo-electric effect.…”

Section: Discussionmentioning

confidence: 99%

“…In order to measure the operator σ n , i.e., the spin projection onto the axis n, we first apply a 'magnetic field' h = hn directed along n. This is achieved via proper charge-and flux-biasing as described by the equations (32). The doublet space {|+ , |− } then is split with new qubit eigenstates |+ n and |− n separated by the 'Zeeman' energy ∆E = 2h.…”

Section: A Measurements In the Qubit's Eigenbasismentioning

confidence: 99%

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Superconducting Tetrahedral Quantum Bits

et al. 2004

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We propose a new design for a quantum bit with four superconducting islands in the topology of a symmetric tetrahedron, uniformly frustrated with one-half flux-quantum per loop and one-half Cooper-pair per island. This structure emulates a noise-resistant spin-1/2 system in a vanishing magnetic field. The tetrahedral quantum bit combines a number of advances such as a doubly degeneracy ground state minimizing decoherence via phonon radiation, a weak quadratic sensitivity to electric and magnetic noise, relieved constraints on the junction fabrication, a large freedom in manipulation, and attractive measurement schemes. The simultaneous appearance of a degenerate ground state and a weak noise sensitivity are consequences of the tetrahedral symmetry, while enhanced quantum fluctuations derive from the special magnetic frustration. We determine the spectral properties of the tetrahedral structure within a semiclassical analysis and confirm the results numerically. We show how proper tuning of the charge-frustration selects a doubly degenerate ground state and discuss the qubit's manipulation through capacitive and inductive coupling to external bias sources. The complete readout of the spin-components σi, i = x, y, z, is achieved through coupling of the internal qubit currents to external junctions driven close to criticality during the measurement.

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Decoherence in Superconducting Quantum Bits by Phonon Radiation

Cited by 54 publications

References 21 publications

Superconducting phase qubits

Superconducting phase qubits

Quantum acoustics with superconducting qubits

Superconducting Tetrahedral Quantum Bits

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