scholarly journals Towards practical quantum computers: transmon qubit with a lifetime approaching 0.5 milliseconds

2022 ◽  
Vol 8 (1) ◽  
Author(s):  
Chenlu Wang ◽  
Xuegang Li ◽  
Huikai Xu ◽  
Zhiyuan Li ◽  
Junhua Wang ◽  
...  
Keyword(s):  
Large Scale ◽  
Dry Etching ◽  
Wet Etching ◽  
Etching Process ◽  
Quantum Circuits ◽  
Quantum Computers ◽  
Tantalum Films ◽  
Long Lifetime ◽  
Superconducting Quantum Circuits

AbstractHere we report a breakthrough in the fabrication of a long lifetime transmon qubit. We use tantalum films as the base superconductor. By using a dry etching process, we obtained transmon qubits with a best T1 lifetime of 503 μs. As a comparison, we also fabricated transmon qubits with other popular materials, including niobium and aluminum, under the same design and fabrication processes. After characterizing their coherence properties, we found that qubits prepared with tantalum films have the best performance. Since the dry etching process is stable and highly anisotropic, it is much more suitable for fabricating complex scalable quantum circuits, when compared to wet etching. As a result, the current breakthrough indicates that the dry etching process of tantalum film is a promising approach to fabricate medium- or large-scale superconducting quantum circuits with a much longer lifetime, meeting the requirements for building practical quantum computers.

Study on the Etching Technique of Non-Photosensitive Polyimide

2015 ◽  
Vol 645-646 ◽  
pp. 163-168
Author(s):  
Rui Lei ◽  
Wei Guo Liu ◽  
Chang Long Cai ◽  
Shun Zhou ◽  
Jing Nie ◽  
...  
Keyword(s):  
Bias Voltage ◽  
Sacrificial Layer ◽  
Dry Etching ◽  
Wet Etching ◽  
Etching Process ◽  
Good Effect ◽  
Floating Structure ◽  
Etching Technique ◽  
Layer Material ◽  
Etching Effect

Polyimide is often used as a sacrificial layer material to make floating structure. Polyimide is also divided into photosensitive and non-photosensitive type; photosensitive polyimide currently has more negative photoresist and poor performance in many ways. Compared with photosensitive polyimide, the non-photosensitive type has low stress, stable performance and other advantages, so non-photosensitive polyimide has been chosen as a sacrificial layer material. To achieve the graphical function and release sacrificial layer, A deeply research was made in this dissertation makes on wet etching and dry etching. By controlling the wet etching process of prebake condition, exposure and developing time, and oxygen dry etching process of etching power, bias voltage and other key process parameters, a good sacrificial layer graph and etching effect have been got. Finally, it can be concluded that when the prebake conditions for 105°C, 8min and times of exposure and developing were 11s and 29s, the non-photosensitive polyimide wet etching effect is the best; when the etching power is 1000w, an oxygen flux rate is 50sccm, the reaction pressure is 30mTorr, the bias voltage is 140v, oxygen dry etching has a good effect.

scholarly journals Quantum Factoring Algorithm: Resource Estimation and Survey of Experiments

2020 ◽  
pp. 39-55
Author(s):  
Noboru Kunihiro
Keyword(s):  
Large Scale ◽  
Quantum Circuit ◽  
The Other ◽  
Quantum Circuits ◽  
Small Scale ◽  
Quantum Computers ◽  
Resource Estimation ◽  
Shor's Algorithm ◽  
Order Of An Element ◽  
Factoring Algorithm

Abstract It is known that Shor’s algorithm can break many cryptosystems such as RSA encryption, provided that large-scale quantum computers are realized. Thus far, several experiments for the factorization of the small composites such as 15 and 21 have been conducted using small-scale quantum computers. In this study, we investigate the details of quantum circuits used in several factoring experiments. We then indicate that some of the circuits have been constructed under the condition that the order of an element modulo a target composite is known in advance. Because the order must be unknown in the experiments, they are inappropriate for designing the quantum circuit of Shor’s factoring algorithm. We also indicate that the circuits used in the other experiments are constructed by relying considerably on the target composite number to be factorized.

scholarly journals Modeling Enclosures for Large-Scale Superconducting Quantum Circuits

2020 ◽  
Vol 14 (2) ◽  
Author(s):  
P.A. Spring ◽  
T. Tsunoda ◽  
B. Vlastakis ◽  
P.J. Leek
Keyword(s):  
Large Scale ◽  
Quantum Circuits ◽  
Superconducting Quantum Circuits

scholarly journals Cost function dependent barren plateaus in shallow parametrized quantum circuits

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
M. Cerezo ◽  
Akira Sone ◽  
Tyler Volkoff ◽  
Lukasz Cincio ◽  
Patrick J. Coles
Keyword(s):  
Cost Function ◽  
Large Scale ◽  
Quantum Algorithms ◽  
Quantum Circuit ◽  
Quantum Circuits ◽  
Quantum Computers ◽  
Heuristic Methods ◽  
Practical Applications ◽  
Local Observables ◽  
Large Scale Simulations

AbstractVariational quantum algorithms (VQAs) optimize the parameters θ of a parametrized quantum circuit V(θ) to minimize a cost function C. While VQAs may enable practical applications of noisy quantum computers, they are nevertheless heuristic methods with unproven scaling. Here, we rigorously prove two results, assuming V(θ) is an alternating layered ansatz composed of blocks forming local 2-designs. Our first result states that defining C in terms of global observables leads to exponentially vanishing gradients (i.e., barren plateaus) even when V(θ) is shallow. Hence, several VQAs in the literature must revise their proposed costs. On the other hand, our second result states that defining C with local observables leads to at worst a polynomially vanishing gradient, so long as the depth of V(θ) is $${\mathcal{O}}(\mathrm{log}\,n)$$ O ( log n ) . Our results establish a connection between locality and trainability. We illustrate these ideas with large-scale simulations, up to 100 qubits, of a quantum autoencoder implementation.

Erratum: Dry etching process for fabrication of optoelectronic gratings in III-V substrates

1992 ◽  
Vol 28 (3) ◽  
pp. 338
Author(s):  
A.S. Gozdz ◽  
J.A. Shelburne ◽  
R.S. Robinson ◽  
C.C. Chang
Keyword(s):  
Dry Etching ◽  
Etching Process

scholarly journals Andreev Probe of Persistent Current States in Superconducting Quantum Circuits

2005 ◽  
Vol 95 (14) ◽  
Author(s):  
V. T. Petrashov ◽  
K. G. Chua ◽  
K. M. Marshall ◽  
R. Sh. Shaikhaidarov ◽  
J. T. Nicholls
Keyword(s):  
Persistent Current ◽  
Quantum Circuits ◽  
Superconducting Quantum Circuits

scholarly journals Fully in situ Nb/InAs-nanowire Josephson junctions by selective-area growth and shadow evaporation

2021 ◽  
Author(s):  
Pujitha Perla ◽  
H. Aruni Fonseka ◽  
Patrick Zellekens ◽  
Russell Deacon ◽  
Yisong Han ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Josephson Junctions ◽  
Quantum Circuits ◽  
Selective Area Growth ◽  
Selective Area ◽  
Area Growth ◽  
Shadow Evaporation ◽  
Superconducting Quantum Circuits

Nb/InAs-nanowire Josephson junctions are fabricated in situ by a special shadow evaporation scheme for the superconducting Nb electrode. The junctions are interesting candidates for superconducting quantum circuits requiring large magnetic fields.

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