Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Chinese Physics Letters

Anomalous Temperature Dependence of the Quality Factor in a Superconducting Coplanar Waveguide Resonator

Pin-Jia Zhou, Yiwen Wang, Lian-Fu Wei

Published Jun 1, 2014• 2 citations
Publisher

Abstract

We present the measurements of the temperature dependence of the internal quality factor ( Q i ) of a microwave resonator, well below the superconducting transition temperature. The device is a quarter-wavelength niobium ( T c = 9.2 K) coplanar waveguide resonator. The measured | S 21 | parameter shows typically the skewed Lorentzian distributions, from which the fitted quality factor monotonically decreases with the temperature increasing from 30 mK to 900 mK. It is observed that for the lower temperature range (i.e., at T < 700 mK) the temperature dependence of the fitted Q i deviates significantly from the predictions of the usual Mattis—Bardeen theory. The measured 3 dB internal quality factor Q ′ i also verifies such an anomalous temperature dependence. Physically, this phenomenon could be attributed dominantly to the effects of the two-level systems in the device, rather than the usual temperature-dependent complex conductance.

DOI
10.1088/0256-307x/31/6/067402

Related papers

Power and temperature dependent model for high Q superconductor resonators

Ashish Alexander, Christopher Weddle, Christopher J. K. Richardson

Measuring the internal quality factor of coplanar waveguide superconducting resonators is an established method of determining small losses in superconducting devices. Often, resonator losses are attributed to two-level system (TLS) defects using a power dependent model for the quality factor. However, excess non-equilibrium quasiparticles can also limit the quality factor of superconducting resonators. Here, a two-temperature, power and temperature dependent model is used to evaluate resonator losses for titanium nitride and aluminum coplanar waveguide resonators with loss tangents of 10−5–10−6. This model enables a set of parameters to describe both the internal quality factor and fractional frequency shift of the resonator across a broad range of average cavity photon numbers, from 1 to 106, and temperatures between those limited by the experimental apparatus near 50 mK and thermal quasiparticle dominated. The presented model also offers potential insight into observing the temperature and power dependence of TLS–TLS interactions in these resonators.

arXiv:2205.06291•APL Quantum•Jul 23, 2025•4 citations

Characterizing Niobium Nitride Superconducting Microwave Coplanar Waveguide Resonator Array for Circuit Quantum Electrodynamics in Extreme Conditions

Paniz Foshat, Paul Baity, Sergey Danilin +9 more

The high critical magnetic field and relatively high critical temperature of niobium nitride (NbN) make it a promising material candidate for applications in superconducting quantum technology. However, NbN-based devices and circuits are sensitive to decoherence sources such as two-level system (TLS) defects. Here, we numerically and experimentally investigate NbN superconducting microwave coplanar waveguide resonator arrays, with a 100 nm thickness, capacitively coupled to a common coplanar waveguide on a silicon chip. We observe that the resonators' internal quality factor (Qi) decreases from Qi ~ 1.07*10^6 in a high power regime (< nph > = 27000) to Qi ~ 1.36 *10^5 in single photon regime at temperature T = 100 mK. Data from this study is consistent with the TLS theory, which describes the TLS interactions in resonator substrates and interfaces. Moreover, we study the temperature dependence internal quality factor and frequency tuning of the coplanar waveguide resonators to characterise the quasiparticle density of NbN. We observe that the increase in kinetic inductance at higher temperatures is the main reason for the frequency shift. Finally, we measure the resonators' resonance frequency and internal quality factor at single photon regime in response to in-plane magnetic fields B||. We verify that Qi stays well above 10^4 up to B|| = 240 mT in the photon number < nph > = 1.8 at T = 100 mK. Our results may pave the way for realising robust microwave superconducting circuits for circuit quantum electrodynamics (cQED) at high magnetic fields necessary for fault-tolerant quantum computing, and ultrasensitive quantum sensing.

arXiv:2306.02356•Jun 4, 2023•1 citation

Temperature and power characteristics of quarter-wavelength superconducting coplanar waveguide resonator

Huilong Yu, Lingxiao Jing, Tao Hua +1 more

Abstract A quarter wavelength superconducting aluminum film coplanar waveguide resonator with a high-quality factor was designed and fabricated. Furthermore, its resonant frequency and quality as a function of temperatures and exciting powers were investigated. The experimental results showed that the resonance frequency decreases about 1% with the increase of temperature from 50 mk to 1 K, and the load quality factor of the resonator also decreases. The resonant frequency decreases with power from − 120 to − 70 dBm. The quality factor increases with increased excitation power due to the loss decreases and nonlinearity. The results are consistent with the theoretical analysis of the surface impedance model.

SN Applied Sciences•Feb 2, 2022•2 citations

Power-dependence measurement of the quality factor of superconducting microwave resonators at mK temperature

Seon Hoo Kim, Dong-Gwang Ha, Gwan Yeol Park +7 more

We report our setup and measurement results of the quality factor Q of superconducting microwave resonators at mK temperature in a dilution refrigerator. The power dependence of the superconducting resonators' Q was measured down to the single photon level. Measurements were performed on two types of microwave resonators. First, a half-wavelength coplanar waveguide (CPW) resonator made of niobium film on an oxidized high-resistivity silicon substrate was measured. Then a rectangular box resonator made of machined superconducting aluminum alloy was measured. While the CPW chip resonator's Q value showed noticeable decrease at low microwave power, the box resonator's Q showed little power dependence. This setup is intended to perform characterization of various microwave resonators, which will serve as key components in superconducting qubit in circuit QED architecture.

Conference on Precision Electromagnetic Measurements•Aug 1, 2014•2 citations

Microwave transmissions through superconducting coplanar waveguide resonators with different coupling configurations

Zhang Si-Lei, Li Hai-Jie, L. F. Wei +6 more

We design and fabricate two types of superconducting niobium coplanar waveguide microwave resonators with different coupling capacitors on high purity Si substrates. Their microwave transmissions are measured at the temperatures of 20 mK. It is found that these two types of resonators possess significantly-different loaded quality factors; one is $5.6\times{10}^{3}$, and the other is $4.0\times{10}^{4}$. The measured data are fitted well by classical ABCD matrix approach. We found that the transmission peak deviates from the standard Lorentizian with a frequency broadening.

arXiv:1304.2900•Apr 10, 2013•0 citations

Anomalous Microwave Response in YBCO Resonators beyond the Two-Level-System Model

Kaiwen Zheng, Nathan J. Johnson, Nathan T. Thobaben +5 more

We report the microwave response of coplanar-waveguide (CPW) resonators fabricated from $\mathrm{YBa_2Cu_3O_{7-δ}}$ (YBCO) thin films over temperatures from approximately $70~\mathrm{mK}$ to $40~\mathrm{K}$. The resonators exhibit internal quality factors $Q_\mathrm{i}$ in the range of $4\times10^3$ to $10^4$ at 70 mK, which increase to a maximum of approximately $8\times10^3$ to $1.2\times10^4$ near $6~\mathrm{K}$. At low temperatures, both $Q_\mathrm{i}$ and the fractional shift of the resonance frequency $Δf_\mathrm{r}/f_\mathrm{r}$ increases with temperature, qualitatively resembling behavior commonly associated with two-level-system (TLS) defects. However, neither response saturates on the temperature scale set by the resonator frequency, and the loss exhibits no observable microwave-power dependence. We show that low-temperature frequency upturn may be better described by an additional paramagnetic response associated with defect-induced local moments or Andreev bound states, while the low-temperature loss follows an approximately logarithmic temperature dependence whose microscopic origin remains unresolved. These measurements establish the millikelvin performance of patterned YBCO resonators and show that their low-temperature response cannot be understood within the conventional TLS framework alone.

cond-mat.supr-conCross-listedarXiv:2607.27392•Jul 31, 2026•0 citations
We present the measurements of the temperature dependence of the internal quality factor ( Q i ) of a microwave resonator, well below the superconducting transition temperature. The device is a quarter-wavelength niobium ( T c = 9.2 K) coplanar waveguide resonator. The measured | S 21 | parameter shows typically the skewed Lorentzian distributions, from which the fitted quality factor monotonically decreases with the temperature increasing from 30 mK to 900 mK. It is observed that for the lower temperature range (i.e., at T < 700 mK) the temperature dependence of the fitted Q i deviates significantly from the predictions of the usual Mattis—Bardeen theory. The measured 3 dB internal quality factor Q ′ i also verifies such an anomalous temperature dependence. Physically, this phenomenon could be attributed dominantly to the effects of the two-level systems in the device, rather than the usual temperature-dependent complex conductance.
Measuring the internal quality factor of coplanar waveguide superconducting resonators is an established method of determining small losses in superconducting devices. Often, resonator losses are attributed to two-level system (TLS) defects using a power dependent model for the quality factor. However, excess non-equilibrium quasiparticles can also limit the quality factor of superconducting resonators. Here, a two-temperature, power and temperature dependent model is used to evaluate resonator losses for titanium nitride and aluminum coplanar waveguide resonators with loss tangents of 10−5–10−6. This model enables a set of parameters to describe both the internal quality factor and fractional frequency shift of the resonator across a broad range of average cavity photon numbers, from 1 to 106, and temperatures between those limited by the experimental apparatus near 50 mK and thermal quasiparticle dominated. The presented model also offers potential insight into observing the temperature and power dependence of TLS–TLS interactions in these resonators.
The high critical magnetic field and relatively high critical temperature of niobium nitride (NbN) make it a promising material candidate for applications in superconducting quantum technology. However, NbN-based devices and circuits are sensitive to decoherence sources such as two-level system (TLS) defects. Here, we numerically and experimentally investigate NbN superconducting microwave coplanar waveguide resonator arrays, with a 100 nm thickness, capacitively coupled to a common coplanar waveguide on a silicon chip. We observe that the resonators' internal quality factor (Qi) decreases from Qi ~ 1.07*10^6 in a high power regime (< nph > = 27000) to Qi ~ 1.36 *10^5 in single photon regime at temperature T = 100 mK. Data from this study is consistent with the TLS theory, which describes the TLS interactions in resonator substrates and interfaces. Moreover, we study the temperature dependence internal quality factor and frequency tuning of the coplanar waveguide resonators to characterise the quasiparticle density of NbN. We observe that the increase in kinetic inductance at higher temperatures is the main reason for the frequency shift. Finally, we measure the resonators' resonance frequency and internal quality factor at single photon regime in response to in-plane magnetic fields B||. We verify that Qi stays well above 10^4 up to B|| = 240 mT in the photon number < nph > = 1.8 at T = 100 mK. Our results may pave the way for realising robust microwave superconducting circuits for circuit quantum electrodynamics (cQED) at high magnetic fields necessary for fault-tolerant quantum computing, and ultrasensitive quantum sensing.
Abstract A quarter wavelength superconducting aluminum film coplanar waveguide resonator with a high-quality factor was designed and fabricated. Furthermore, its resonant frequency and quality as a function of temperatures and exciting powers were investigated. The experimental results showed that the resonance frequency decreases about 1% with the increase of temperature from 50 mk to 1 K, and the load quality factor of the resonator also decreases. The resonant frequency decreases with power from − 120 to − 70 dBm. The quality factor increases with increased excitation power due to the loss decreases and nonlinearity. The results are consistent with the theoretical analysis of the surface impedance model.
We report our setup and measurement results of the quality factor Q of superconducting microwave resonators at mK temperature in a dilution refrigerator. The power dependence of the superconducting resonators' Q was measured down to the single photon level. Measurements were performed on two types of microwave resonators. First, a half-wavelength coplanar waveguide (CPW) resonator made of niobium film on an oxidized high-resistivity silicon substrate was measured. Then a rectangular box resonator made of machined superconducting aluminum alloy was measured. While the CPW chip resonator's Q value showed noticeable decrease at low microwave power, the box resonator's Q showed little power dependence. This setup is intended to perform characterization of various microwave resonators, which will serve as key components in superconducting qubit in circuit QED architecture.
We design and fabricate two types of superconducting niobium coplanar waveguide microwave resonators with different coupling capacitors on high purity Si substrates. Their microwave transmissions are measured at the temperatures of 20 mK. It is found that these two types of resonators possess significantly-different loaded quality factors; one is 5.6×1035.6\times{10}^{3}5.6×103, and the other is 4.0×1044.0\times{10}^{4}4.0×104. The measured data are fitted well by classical ABCD matrix approach. We found that the transmission peak deviates from the standard Lorentizian with a frequency broadening.
We report the microwave response of coplanar-waveguide (CPW) resonators fabricated from YBa2Cu3O7−δ\mathrm{YBa_2Cu_3O_{7-δ}}YBa2​Cu3​O7−δ​ (YBCO) thin films over temperatures from approximately 70 mK70~\mathrm{mK}70 mK to 40 K40~\mathrm{K}40 K. The resonators exhibit internal quality factors QiQ_\mathrm{i}Qi​ in the range of 4×1034\times10^34×103 to 10410^4104 at 70 mK, which increase to a maximum of approximately 8×1038\times10^38×103 to 1.2×1041.2\times10^41.2×104 near 6 K6~\mathrm{K}6 K. At low temperatures, both QiQ_\mathrm{i}Qi​ and the fractional shift of the resonance frequency Δfr/frΔf_\mathrm{r}/f_\mathrm{r}Δfr​/fr​ increases with temperature, qualitatively resembling behavior commonly associated with two-level-system (TLS) defects. However, neither response saturates on the temperature scale set by the resonator frequency, and the loss exhibits no observable microwave-power dependence. We show that low-temperature frequency upturn may be better described by an additional paramagnetic response associated with defect-induced local moments or Andreev bound states, while the low-temperature loss follows an approximately logarithmic temperature dependence whose microscopic origin remains unresolved. These measurements establish the millikelvin performance of patterned YBCO resonators and show that their low-temperature response cannot be understood within the conventional TLS framework alone.