Entanglement across separate silicon dies in a modular superconducting qubit device (original) (raw)
Related papers
Genuine 12-Qubit Entanglement on a Superconducting Quantum Processor
Physical Review Letters
We report the preparation and verification of a genuine 12-qubit entanglement in a superconducting processor. The processor that we designed and fabricated has qubits lying on a 1D chain with relaxation times ranging from 29.6 to 54.6 μs. The fidelity of the 12-qubit entanglement was measured to be above 0.5544 AE 0.0025, exceeding the genuine multipartite entanglement threshold by 21 statistical standard deviations. After thermal cycling, the 12-qubit state fidelity was further improved to be above 0.707 AE 0.008. Our entangling circuit to generate linear cluster states is depth invariant in the number of qubits and uses single-and double-qubit gates instead of collective interactions. Our results are a substantial step towards large-scale random circuit sampling and scalable measurement-based quantum computing.
Two-qubit entangling gates for superconducting quantum computers
Results in Physics, 2024
Noisy intermediate-scale quantum computers (NISQ) have demonstrated superior performance compared to conventional computing schemes. Nonetheless, errors associated with two-qubit entangling gates remain a substantial obstacle in fully harnessing the potential of current superconducting quantum computers. The achievement of quantum computation and quantum information processing critically depends on the presence of entangled states. These states are indispensable for quantum computers to surpass classical computers in terms of computational power. This paper presents a comprehensive characterization of a two-qubit entangling gate, known as Dagwood Bumstead (DB) gate, to investigate the challenges posed by errors in the DB gate on NISQ devices. Firstly, we propose a scheme for the realization of the DB gate using two capacitively coupled Josephson Superconducting qubits, based on the experimental setup carried out in Bialczak et al. (2010). Additionally, we introduce and characterize a novel two-qubit quantum gate. Our proposed gate showcases an impressive average gate fidelity of 0.85450. The DB gate's performance is fully described through quantum process tomography (QPT) and quantum state tomography (QST) experiments conducted in three different environments: noisy, noiseless, and on a real IBM quantum computer. The process fidelity of the DB gate is measured to be 0.8069705, and the state fidelity is determined to be 0.8858750. This study offers valuable insights into the performance of the DB gate on a NISQ device, showcasing its potential for executing intricate algorithms and operations on an authentic quantum computer.
Building blocks of a flip-chip integrated superconducting quantum processor
Quantum Science and Technology
We have integrated single and coupled superconducting transmon qubits into flip-chip modules. Each module consists of two chips—one quantum chip and one control chip—that are bump-bonded together. We demonstrate time-averaged coherence times exceeding 90 μs, single-qubit gate fidelities exceeding 99.9%, and two-qubit gate fidelities above 98.6%. We also present device design methods and discuss the sensitivity of device parameters to variation in interchip spacing. Notably, the additional flip-chip fabrication steps do not degrade the qubit performance compared to our baseline state-of-the-art in single-chip, planar circuits. This integration technique can be extended to the realisation of quantum processors accommodating hundreds of qubits in one module as it offers adequate input/output wiring access to all qubits and couplers.
Demonstration of two-qubit algorithms with a superconducting quantum processor
Nature, 2009
By harnessing the superposition and entanglement of physical states, quantum computers could outperform their classical counterparts in solving problems of technological impact, such as factoring large numbers and searching databases 1,2 . A quantum processor executes algorithms by applying a programmable sequence of gates to an initialized register of qubits, which coherently evolves into a final state containing the result of the computation. Simultaneously meeting the conflicting requirements of long coherence, state preparation, universal gate operations, and qubit readout makes building quantum processors challenging. Few-qubit processors have already been shown in nuclear magnetic resonance 3,4,5,6 , cold ion trap 7,8 and optical 9 systems, but a solid-state realization has remained an outstanding challenge.
Tunable coupling between three qubits as a building block for a superconducting quantum computer
Physical Review B, 2011
Large scale quantum computers will consist of many interacting qubits. In this paper we expand the two flux qubit coupling scheme first devised in [Phys. Rev. B 70, 140501 (2004)] and realized in [Science 314, 1427[Science 314, (2006] to a three-qubit, two-coupler scenario. We study L-shaped and lineshaped coupler geometries, and show how the interaction strength between qubits changes in terms of the couplers' dimensions. We explore two cases: the "on-state" where the interaction energy between two nearest-neighbor qubits is high, and the "off-state" where it is turned off. In both situations we study the undesirable crosstalk with the third qubit. Finally, we use the GRAPE algorithm to find efficient pulse sequences for two-qubit gates subject to our calculated physical constraints on the coupling strength.
Measurement of the Entanglement of Two Superconducting Qubits via State Tomography
Science, 2006
The laws of quantum physics provide intriguing possibilities for a tremendous increase in speed compared to classical computation 1 . Because this power is achieved through the controlled evolution of entangled quantum states, a clear demonstration of entanglement represents a key milestone towards the construction of a scalable quantum computer 2,3 . Although entanglement can be inferred from simple experiments, a direct demonstration is challenging because all of the DiVincenzo criteria 4 for quantum computation must be met simultaneously. Only subsets of these key requirements have been demonstrated previously for superconducting qubits 5-9 . Here, we demonstrate all of the DiVincenzo criteria simultaneously, thus taking a significant step forward towards placing superconducting qubits on the roadmap for scalable quantum computing. Specifically, capacitively-coupled Josephson phase qubits are used to create Bell states, which when measured using state tomography on both qubits show an entangled state with fidelity of up to 87%. Our results demonstrate a high degree of unitary control of the system, indicating that larger implementations are within reach. Circuits made of superconductors and Josephson junctions are promising candidates for scalable quantum computation because of their compatibility with integrated-circuit fabrication technology 5-9 . The Josephson phase qubit stands apart from other 2. Häffner, H. et al. Scalable multiparticle entanglement of trapped ions. Nature 438, 643-646 (2005) 3. Leibfried, D. et al. Creation of a six-atom 'Schrödinger cat' state. Nature 438, 639-642 (2005) 4. DiVincenzo, D. P. The physical implementation of quantum computers. Fortschr. Physik 48, 771-783 (2000). 5. McDermott, R. et al. Simultaneous state measurement of coupled Josephson phase qubits. Science 307, 1299-1302 (2005) 6. Yamamoto, T. et al. Demonstration of conditional gate operation using superconducting charge qubits. Nature 425, 941-944 (2003) 7. Vion, D. et al. Manipulating the quantum state of an electrical circuit. Science 296, 886-889 (2002)
Wiring Up Superconducting Qubits
2015
A qubit made of a semiconducting nanowire sandwiched between two superconductors could simplify the design of quantum information processing architectures.
Low-loss interconnects for modular superconducting quantum processors
Nature Electronics
Yo.Z. conceived the idea and supervised the experiment. S.L. supervised the device fabrication and supported the infrastructure setup. J.N. and Yo.Z. wirebonded the cables, performed the measurement and analyzed the data. L.Z. fabricated the devices and designed the sample holder. Y.L. and J.Q. assisted the measurement. Yo.Z. built the custom microwave electronics. Yo.Z. and A.N.C wrote the manuscript. All authors contributed to discussions and production of the manuscript.
2016
Quantum error-correction codes would protect an arbitrary state of a multi-qubit register against decoherence-induced errors 1 , but their implementation is an outstanding challenge for the development of large-scale quantum computers. A first step is to stabilize a nonequilibrium state of a simple quantum system such as a qubit or a cavity mode in the presence of decoherence. Several groups have recently accomplished this goal using measurementbased feedback schemes 2-5. A next step is to prepare and stabilize a state of a composite system 6-8. Here we demonstrate the stabilization of an entangled Bell state of a quantum register of two superconducting qubits for an arbitrary time. Our result is achieved by an autonomous feedback scheme which combines continuous drives along with a specifically engineered coupling between the two-qubit register and a dissipative reservoir. Similar autonomous feedback techniques have recently been used for qubit reset 9 and the stabilization of a single qubit state 10 , as well as for creating 11 and stabilizing 6 states of multipartite quantum systems. Unlike conventional, measurement-based schemes, an autonomous approach counter-intuitively uses engineered dissipation to fight decoherence 12-15 , obviating the need 1