Raymond Simmonds - Academia.edu (original) (raw)
Papers by Raymond Simmonds
arXiv (Cornell University), Apr 16, 2009
When a three-level quantum system is irradiated by an intense coupling field resonant with one of... more When a three-level quantum system is irradiated by an intense coupling field resonant with one of the three possible transitions, the absorption peak of an additional probe field involving the remaining level is split. This process is known in quantum optics as the Autler-Townes effect. We observe these phenomena in a superconducting Josephson phase qubit, which can be considered an "artificial atom" with a multilevel quantum structure. The spectroscopy peaks can be explained reasonably well by a simple three-level Hamiltonian model. Simulation of a more complete model (including dissipation, higher levels, and cross-coupling) provides excellent agreement with all the experimental data.
Physical Review Letters, Apr 16, 2009
When a three-level quantum system is irradiated by an intense coupling field resonant with two of... more When a three-level quantum system is irradiated by an intense coupling field resonant with two of the three possible transitions, the resonant absorption of the system from its ground state by an additional radiation field is suppressed. This effect, where the population is trapped in the ground state, is known in quantum optics as "electromagnetically induced transparency". When the coupling field is detuned from resonance, the resonant absorption peak splits to form an "Autler-Townes doublet". We observe these phenomena in a superconducting Josephson phase qubit, which can be considered an "artificial atom" with a multilevel quantum structure. These observations are qualitatively described by a simple model restricted to three energy levels. A full solution of the master equation including higher levels provides excellent agreement with all the experimental data.
Nature, Aug 1, 2010
Multipartite entanglement is essential for quantum computation 1 and communication 2-4 , and for ... more Multipartite entanglement is essential for quantum computation 1 and communication 2-4 , and for fundamental tests of quantum mechanics 5 and precision measurements 6. It has been achieved with various forms of quantum bits (qubits), such as trapped ions 7,8 , photons 9 and atoms passing through microwave cavities 10. Quantum systems based on superconducting circuits, which are potentially more scalable, have been used to control pair-wise interactions of qubits 11-16 and spectroscopic evidence for three-particle entanglement was observed 17,18. Here, we report the demonstration of coherent interactions in the time domain for three directly coupled superconducting quantum systems, two phase qubits and one resonant cavity. We provide evidence for the deterministic evolution from a simple product state, through a tripartite W state, into a (bipartite) Bell state. The cavity can be thought of as a multiphoton register or an entanglement bus, and arbitrary preparation of multiphoton states in this cavity using one of the qubits 19 and subsequent interactions for entanglement distribution should allow for the deterministic creation of another class of entanglement, a Greenberger-Horne-Zeilinger state. With the development of quantum information science 1 , entanglement of multiparticle systems has become a resource for a new information technology. In particular, three-particle or tripartite entanglement allows for teleportation 2 , secret sharing 4 and dense coding 20 , with connections to cosmology 21. Over the past decade, the development of exquisite control over quantum systems has led to various demonstrations of tripartite entanglement 8-10. Genuine tripartite entanglement is delineated by two inequivalent classes of states 22 : Greenberger-Horne-Zeilinger and W, where the W state involves only a single photon shared amongst three systems. Using multipartite entanglement in a solid-state-qubit system has only recently received theoretical attention 23-25. Thus far in superconducting systems, bipartite entanglement has been verified by two-qubit quantum state tomography 13 and used to carry out a quantum algorithm 15. Spectroscopic evidence for three-particle entanglement was observed for two current-biased phase qubits coupled to a lumped element consisting of an inductor-capacitor circuit and a cavity as well as for transmon qubits 17,18. In the experiments described below, we first verified the spectroscopic signature of three coupled systems. Next, we demonstrated coherent interactions. Frequency detuning of the third system was used to verify the proper change in the time evolution of two versus three coupled systems. Finally, we describe a free-evolution process as a means of deterministically preparing arbitrary single-photon tripartite entangled states and a corresponding visualization LETTERS NATURE PHYSICS
Bulletin of the American Physical Society, Mar 12, 2008
Bulletin of the American Physical Society, Mar 11, 2008
One of the biggest problems facing the fabrication of quantum computers based on superconducting ... more One of the biggest problems facing the fabrication of quantum computers based on superconducting qubits is the short coherence time of the quantum states. This is due to interaction of qubits with both the environment and defects (two level systems-TLS) in the Josephson junction (JJ). Because of the large JJ area, this problem is particularly obvious in phase qubits where it has been shown that TLS greatly affect the coherence time. 2 One way to overcome this problem is to reduce the size of the JJ thus reducing the number of TLS. 3 We will discuss the results of our approach to this solution, namely using shadow evaporated JJ (< 1µm 2) and low-loss capacitor, and the results of our experiments on coupled qubits.
Physical Review Letters, Apr 29, 2010
We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumped eleme... more We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumped element resonator. The coupling strength is mediated by a flux-biased RF SQUID operated in the nonhysteretic regime. By tuning the applied flux bias to the RF SQUID we change the effective mutual inductance, and thus the coupling energy, between the phase qubit and resonator. We verify the modulation of coupling strength from 0 to 100 M Hz by observing modulation in the size of the splitting in the phase qubit's spectroscopy, as well as coherently by observing modulation in the vacuum Rabi oscillation frequency when on resonance. The measured spectroscopic splittings and vacuum Rabi oscillations agree well with theoretical predictions. 1000 pH, Cr 0.4 pF , and Mcr 60 pH. (b) Optical micrograph of the circuit.
Bulletin of the American Physical Society, Mar 12, 2008
Bulletin of the American Physical Society, Mar 17, 2009
CO (USA)-Quantum information theory suggests that there are two inequivalent classes of tripartit... more CO (USA)-Quantum information theory suggests that there are two inequivalent classes of tripartite entanglement under stochastic local operations and classical communications (PRA, 62, 062314). Representative of these classes are the GHZ state and the W states, respectively. In this talk I will describe our experimental results on two superconducting phase qubits coupled through a cavity: one of the few cases where three is company and not a crowd. This system, effectively three coupled qubits if we restrict the cavity excitation to the single photon manifold, has allowed us to observe the spectroscopic signature and dynamics of Tripartite Entanglement. The rich dynamics of this system has allowed us to also observe a) Bell state between two qubits (with the third one disentangled), and b) W state between the three qubits. Future possibilities include the observation of GHZ state, particularly interesting for its practical applications, and for testing the non-locality of quantum mechanics.
Nature Physics, Aug 1, 2010
Multipartite entanglement is essential for quantum computation 1 and communication 2-4 , and for ... more Multipartite entanglement is essential for quantum computation 1 and communication 2-4 , and for fundamental tests of quantum mechanics 5 and precision measurements 6. It has been achieved with various forms of quantum bits (qubits), such as trapped ions 7,8 , photons 9 and atoms passing through microwave cavities 10. Quantum systems based on superconducting circuits, which are potentially more scalable, have been used to control pair-wise interactions of qubits 11-16 and spectroscopic evidence for three-particle entanglement was observed 17,18. Here, we report the demonstration of coherent interactions in the time domain for three directly coupled superconducting quantum systems, two phase qubits and one resonant cavity. We provide evidence for the deterministic evolution from a simple product state, through a tripartite W state, into a (bipartite) Bell state. The cavity can be thought of as a multiphoton register or an entanglement bus, and arbitrary preparation of multiphoton states in this cavity using one of the qubits 19 and subsequent interactions for entanglement distribution should allow for the deterministic creation of another class of entanglement, a Greenberger-Horne-Zeilinger state. With the development of quantum information science 1 , entanglement of multiparticle systems has become a resource for a new information technology. In particular, three-particle or tripartite entanglement allows for teleportation 2 , secret sharing 4 and dense coding 20 , with connections to cosmology 21. Over the past decade, the development of exquisite control over quantum systems has led to various demonstrations of tripartite entanglement 8-10. Genuine tripartite entanglement is delineated by two inequivalent classes of states 22 : Greenberger-Horne-Zeilinger and W, where the W state involves only a single photon shared amongst three systems. Using multipartite entanglement in a solid-state-qubit system has only recently received theoretical attention 23-25. Thus far in superconducting systems, bipartite entanglement has been verified by two-qubit quantum state tomography 13 and used to carry out a quantum algorithm 15. Spectroscopic evidence for three-particle entanglement was observed for two current-biased phase qubits coupled to a lumped element consisting of an inductor-capacitor circuit and a cavity as well as for transmon qubits 17,18. In the experiments described below, we first verified the spectroscopic signature of three coupled systems. Next, we demonstrated coherent interactions. Frequency detuning of the third system was used to verify the proper change in the time evolution of two versus three coupled systems. Finally, we describe a free-evolution process as a means of deterministically preparing arbitrary single-photon tripartite entangled states and a corresponding visualization LETTERS NATURE PHYSICS
Applied Physics Letters, Mar 1, 2010
We have produced high-quality complex microwave circuits, such as multiplexed resonators and supe... more We have produced high-quality complex microwave circuits, such as multiplexed resonators and superconducting phase qubits, using a "vacuum-gap" technology that eliminates lossy dielectric materials. We have improved our design and fabrication strategy beyond our earlier work, leading to increased yield, enabling the realization of these complex circuits. We incorporate both novel vacuum-gap wiring crossovers (VGX) for gradiometric inductors and vacuum-gap capacitors (VGC) on chip to produce resonant circuits that have large internal quality factors (30,000<Q I <165,000) at 50 mK, outperforming most dielectric-filled devices. Resonators with VGCs as large as 180 pF confirm single mode behavior of our lumped-element components.
Bulletin of the American Physical Society, Mar 17, 2010
arXiv (Cornell University), Apr 16, 2010
We report on a method for detecting weakly coupled spurious two-level system fluctuators (TLSs) i... more We report on a method for detecting weakly coupled spurious two-level system fluctuators (TLSs) in superconducting qubits. This method is more sensitive that standard spectroscopic techniques for locating TLSs with a reduced data acquisition time.
Physical Review, Apr 29, 2010
We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumpedelemen... more We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumpedelement resonator. The coupling strength is mediated by a flux-biased rf SQUID operated in the nonhysteretic regime. By tuning the applied flux bias to the rf SQUID we change the effective mutual inductance, and thus the coupling energy, between the phase qubit and resonator. We verify the modulation of coupling strength from 0 to 100 MHz by observing modulation in the size of the splitting in the phase qubit's spectroscopy, as well as coherently by observing modulation in the vacuum Rabi oscillation frequency when on resonance. The measured spectroscopic splittings and vacuum Rabi oscillations agree well with theoretical predictions.
Nature Communications
Quantum reservoir engineering is a powerful framework for autonomous quantum state preparation an... more Quantum reservoir engineering is a powerful framework for autonomous quantum state preparation and error correction. However, traditional approaches to reservoir engineering are hindered by unavoidable coherent leakage out of the target state, which imposes an inherent trade off between achievable steady-state state fidelity and stabilization rate. In this work we demonstrate a protocol that achieves trade off-free Bell state stabilization in a qutrit-qubit system realized on a circuit-QED platform. We accomplish this by creating a purely dissipative channel for population transfer into the target state, mediated by strong parametric interactions coupling the second-excited state of a superconducting transmon and the engineered bath resonator. Our scheme achieves a state preparation fidelity of 84% with a stabilization time constant of 339 ns, leading to a 54 ns error-time product in a solid-state quantum information platform.
We present an experimental demonstration of a phase qubit acting as an ON/OFF switch for the abso... more We present an experimental demonstration of a phase qubit acting as an ON/OFF switch for the absorbtion of photons from an applied probe microwave tone. The control of the switch is achieved through a second microwave tone resonantly coupled to the second transition of the qubit. The ON state is realized when the control tone is sufficiently strong to generate a "dark state" for the qubit, preventing the absorbtion of the probe tone. A three-level model that includes independently determined parameters for relaxation and dephasing gives excellent agreement with the experiment, and allows us to characterize the time-scale for switching.
Boulder-Josephson junctionbased superconducting qubits are still a very promising platform for cr... more Boulder-Josephson junctionbased superconducting qubits are still a very promising platform for creating quantum computers of the future. We have created a strategy to improve the coherence of superconducting phase qubits, through the removal of unwanted two-level system defects known to be a significant source of decoherence. Through creating dielectric free fabrication techniques and vaccum gap capacitors, we can remove a considerable amount of troublesome defects in the construction of phase qubits. Here, we discuss some results and obstacles still facing the design and fabrication of phase qubits.
One of the biggest problems facing the fabrication of quantum computers based on superconducting ... more One of the biggest problems facing the fabrication of quantum computers based on superconducting qubits is the short coherence time of the quantum states. This is due to interaction of qubits with both the environment and defects (two level systems-TLS) in the Josephson junction (JJ). Because of the large JJ area, this problem is particularly obvious in phase qubits where
arXiv (Cornell University), Apr 16, 2009
When a three-level quantum system is irradiated by an intense coupling field resonant with one of... more When a three-level quantum system is irradiated by an intense coupling field resonant with one of the three possible transitions, the absorption peak of an additional probe field involving the remaining level is split. This process is known in quantum optics as the Autler-Townes effect. We observe these phenomena in a superconducting Josephson phase qubit, which can be considered an "artificial atom" with a multilevel quantum structure. The spectroscopy peaks can be explained reasonably well by a simple three-level Hamiltonian model. Simulation of a more complete model (including dissipation, higher levels, and cross-coupling) provides excellent agreement with all the experimental data.
Physical Review Letters, Apr 16, 2009
When a three-level quantum system is irradiated by an intense coupling field resonant with two of... more When a three-level quantum system is irradiated by an intense coupling field resonant with two of the three possible transitions, the resonant absorption of the system from its ground state by an additional radiation field is suppressed. This effect, where the population is trapped in the ground state, is known in quantum optics as "electromagnetically induced transparency". When the coupling field is detuned from resonance, the resonant absorption peak splits to form an "Autler-Townes doublet". We observe these phenomena in a superconducting Josephson phase qubit, which can be considered an "artificial atom" with a multilevel quantum structure. These observations are qualitatively described by a simple model restricted to three energy levels. A full solution of the master equation including higher levels provides excellent agreement with all the experimental data.
Nature, Aug 1, 2010
Multipartite entanglement is essential for quantum computation 1 and communication 2-4 , and for ... more Multipartite entanglement is essential for quantum computation 1 and communication 2-4 , and for fundamental tests of quantum mechanics 5 and precision measurements 6. It has been achieved with various forms of quantum bits (qubits), such as trapped ions 7,8 , photons 9 and atoms passing through microwave cavities 10. Quantum systems based on superconducting circuits, which are potentially more scalable, have been used to control pair-wise interactions of qubits 11-16 and spectroscopic evidence for three-particle entanglement was observed 17,18. Here, we report the demonstration of coherent interactions in the time domain for three directly coupled superconducting quantum systems, two phase qubits and one resonant cavity. We provide evidence for the deterministic evolution from a simple product state, through a tripartite W state, into a (bipartite) Bell state. The cavity can be thought of as a multiphoton register or an entanglement bus, and arbitrary preparation of multiphoton states in this cavity using one of the qubits 19 and subsequent interactions for entanglement distribution should allow for the deterministic creation of another class of entanglement, a Greenberger-Horne-Zeilinger state. With the development of quantum information science 1 , entanglement of multiparticle systems has become a resource for a new information technology. In particular, three-particle or tripartite entanglement allows for teleportation 2 , secret sharing 4 and dense coding 20 , with connections to cosmology 21. Over the past decade, the development of exquisite control over quantum systems has led to various demonstrations of tripartite entanglement 8-10. Genuine tripartite entanglement is delineated by two inequivalent classes of states 22 : Greenberger-Horne-Zeilinger and W, where the W state involves only a single photon shared amongst three systems. Using multipartite entanglement in a solid-state-qubit system has only recently received theoretical attention 23-25. Thus far in superconducting systems, bipartite entanglement has been verified by two-qubit quantum state tomography 13 and used to carry out a quantum algorithm 15. Spectroscopic evidence for three-particle entanglement was observed for two current-biased phase qubits coupled to a lumped element consisting of an inductor-capacitor circuit and a cavity as well as for transmon qubits 17,18. In the experiments described below, we first verified the spectroscopic signature of three coupled systems. Next, we demonstrated coherent interactions. Frequency detuning of the third system was used to verify the proper change in the time evolution of two versus three coupled systems. Finally, we describe a free-evolution process as a means of deterministically preparing arbitrary single-photon tripartite entangled states and a corresponding visualization LETTERS NATURE PHYSICS
Bulletin of the American Physical Society, Mar 12, 2008
Bulletin of the American Physical Society, Mar 11, 2008
One of the biggest problems facing the fabrication of quantum computers based on superconducting ... more One of the biggest problems facing the fabrication of quantum computers based on superconducting qubits is the short coherence time of the quantum states. This is due to interaction of qubits with both the environment and defects (two level systems-TLS) in the Josephson junction (JJ). Because of the large JJ area, this problem is particularly obvious in phase qubits where it has been shown that TLS greatly affect the coherence time. 2 One way to overcome this problem is to reduce the size of the JJ thus reducing the number of TLS. 3 We will discuss the results of our approach to this solution, namely using shadow evaporated JJ (< 1µm 2) and low-loss capacitor, and the results of our experiments on coupled qubits.
Physical Review Letters, Apr 29, 2010
We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumped eleme... more We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumped element resonator. The coupling strength is mediated by a flux-biased RF SQUID operated in the nonhysteretic regime. By tuning the applied flux bias to the RF SQUID we change the effective mutual inductance, and thus the coupling energy, between the phase qubit and resonator. We verify the modulation of coupling strength from 0 to 100 M Hz by observing modulation in the size of the splitting in the phase qubit's spectroscopy, as well as coherently by observing modulation in the vacuum Rabi oscillation frequency when on resonance. The measured spectroscopic splittings and vacuum Rabi oscillations agree well with theoretical predictions. 1000 pH, Cr 0.4 pF , and Mcr 60 pH. (b) Optical micrograph of the circuit.
Bulletin of the American Physical Society, Mar 12, 2008
Bulletin of the American Physical Society, Mar 17, 2009
CO (USA)-Quantum information theory suggests that there are two inequivalent classes of tripartit... more CO (USA)-Quantum information theory suggests that there are two inequivalent classes of tripartite entanglement under stochastic local operations and classical communications (PRA, 62, 062314). Representative of these classes are the GHZ state and the W states, respectively. In this talk I will describe our experimental results on two superconducting phase qubits coupled through a cavity: one of the few cases where three is company and not a crowd. This system, effectively three coupled qubits if we restrict the cavity excitation to the single photon manifold, has allowed us to observe the spectroscopic signature and dynamics of Tripartite Entanglement. The rich dynamics of this system has allowed us to also observe a) Bell state between two qubits (with the third one disentangled), and b) W state between the three qubits. Future possibilities include the observation of GHZ state, particularly interesting for its practical applications, and for testing the non-locality of quantum mechanics.
Nature Physics, Aug 1, 2010
Multipartite entanglement is essential for quantum computation 1 and communication 2-4 , and for ... more Multipartite entanglement is essential for quantum computation 1 and communication 2-4 , and for fundamental tests of quantum mechanics 5 and precision measurements 6. It has been achieved with various forms of quantum bits (qubits), such as trapped ions 7,8 , photons 9 and atoms passing through microwave cavities 10. Quantum systems based on superconducting circuits, which are potentially more scalable, have been used to control pair-wise interactions of qubits 11-16 and spectroscopic evidence for three-particle entanglement was observed 17,18. Here, we report the demonstration of coherent interactions in the time domain for three directly coupled superconducting quantum systems, two phase qubits and one resonant cavity. We provide evidence for the deterministic evolution from a simple product state, through a tripartite W state, into a (bipartite) Bell state. The cavity can be thought of as a multiphoton register or an entanglement bus, and arbitrary preparation of multiphoton states in this cavity using one of the qubits 19 and subsequent interactions for entanglement distribution should allow for the deterministic creation of another class of entanglement, a Greenberger-Horne-Zeilinger state. With the development of quantum information science 1 , entanglement of multiparticle systems has become a resource for a new information technology. In particular, three-particle or tripartite entanglement allows for teleportation 2 , secret sharing 4 and dense coding 20 , with connections to cosmology 21. Over the past decade, the development of exquisite control over quantum systems has led to various demonstrations of tripartite entanglement 8-10. Genuine tripartite entanglement is delineated by two inequivalent classes of states 22 : Greenberger-Horne-Zeilinger and W, where the W state involves only a single photon shared amongst three systems. Using multipartite entanglement in a solid-state-qubit system has only recently received theoretical attention 23-25. Thus far in superconducting systems, bipartite entanglement has been verified by two-qubit quantum state tomography 13 and used to carry out a quantum algorithm 15. Spectroscopic evidence for three-particle entanglement was observed for two current-biased phase qubits coupled to a lumped element consisting of an inductor-capacitor circuit and a cavity as well as for transmon qubits 17,18. In the experiments described below, we first verified the spectroscopic signature of three coupled systems. Next, we demonstrated coherent interactions. Frequency detuning of the third system was used to verify the proper change in the time evolution of two versus three coupled systems. Finally, we describe a free-evolution process as a means of deterministically preparing arbitrary single-photon tripartite entangled states and a corresponding visualization LETTERS NATURE PHYSICS
Applied Physics Letters, Mar 1, 2010
We have produced high-quality complex microwave circuits, such as multiplexed resonators and supe... more We have produced high-quality complex microwave circuits, such as multiplexed resonators and superconducting phase qubits, using a "vacuum-gap" technology that eliminates lossy dielectric materials. We have improved our design and fabrication strategy beyond our earlier work, leading to increased yield, enabling the realization of these complex circuits. We incorporate both novel vacuum-gap wiring crossovers (VGX) for gradiometric inductors and vacuum-gap capacitors (VGC) on chip to produce resonant circuits that have large internal quality factors (30,000<Q I <165,000) at 50 mK, outperforming most dielectric-filled devices. Resonators with VGCs as large as 180 pF confirm single mode behavior of our lumped-element components.
Bulletin of the American Physical Society, Mar 17, 2010
arXiv (Cornell University), Apr 16, 2010
We report on a method for detecting weakly coupled spurious two-level system fluctuators (TLSs) i... more We report on a method for detecting weakly coupled spurious two-level system fluctuators (TLSs) in superconducting qubits. This method is more sensitive that standard spectroscopic techniques for locating TLSs with a reduced data acquisition time.
Physical Review, Apr 29, 2010
We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumpedelemen... more We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumpedelement resonator. The coupling strength is mediated by a flux-biased rf SQUID operated in the nonhysteretic regime. By tuning the applied flux bias to the rf SQUID we change the effective mutual inductance, and thus the coupling energy, between the phase qubit and resonator. We verify the modulation of coupling strength from 0 to 100 MHz by observing modulation in the size of the splitting in the phase qubit's spectroscopy, as well as coherently by observing modulation in the vacuum Rabi oscillation frequency when on resonance. The measured spectroscopic splittings and vacuum Rabi oscillations agree well with theoretical predictions.
Nature Communications
Quantum reservoir engineering is a powerful framework for autonomous quantum state preparation an... more Quantum reservoir engineering is a powerful framework for autonomous quantum state preparation and error correction. However, traditional approaches to reservoir engineering are hindered by unavoidable coherent leakage out of the target state, which imposes an inherent trade off between achievable steady-state state fidelity and stabilization rate. In this work we demonstrate a protocol that achieves trade off-free Bell state stabilization in a qutrit-qubit system realized on a circuit-QED platform. We accomplish this by creating a purely dissipative channel for population transfer into the target state, mediated by strong parametric interactions coupling the second-excited state of a superconducting transmon and the engineered bath resonator. Our scheme achieves a state preparation fidelity of 84% with a stabilization time constant of 339 ns, leading to a 54 ns error-time product in a solid-state quantum information platform.
We present an experimental demonstration of a phase qubit acting as an ON/OFF switch for the abso... more We present an experimental demonstration of a phase qubit acting as an ON/OFF switch for the absorbtion of photons from an applied probe microwave tone. The control of the switch is achieved through a second microwave tone resonantly coupled to the second transition of the qubit. The ON state is realized when the control tone is sufficiently strong to generate a "dark state" for the qubit, preventing the absorbtion of the probe tone. A three-level model that includes independently determined parameters for relaxation and dephasing gives excellent agreement with the experiment, and allows us to characterize the time-scale for switching.
Boulder-Josephson junctionbased superconducting qubits are still a very promising platform for cr... more Boulder-Josephson junctionbased superconducting qubits are still a very promising platform for creating quantum computers of the future. We have created a strategy to improve the coherence of superconducting phase qubits, through the removal of unwanted two-level system defects known to be a significant source of decoherence. Through creating dielectric free fabrication techniques and vaccum gap capacitors, we can remove a considerable amount of troublesome defects in the construction of phase qubits. Here, we discuss some results and obstacles still facing the design and fabrication of phase qubits.
One of the biggest problems facing the fabrication of quantum computers based on superconducting ... more One of the biggest problems facing the fabrication of quantum computers based on superconducting qubits is the short coherence time of the quantum states. This is due to interaction of qubits with both the environment and defects (two level systems-TLS) in the Josephson junction (JJ). Because of the large JJ area, this problem is particularly obvious in phase qubits where