The Experts below are selected from a list of 105459 Experts worldwide ranked by ideXlab platform
Susan N. Coppersmith - One of the best experts on this subject based on the ideXlab platform.
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enhancing the dipolar coupling of a s t 0 Qubit with a transverse sweet spot
Nature Communications, 2019Co-Authors: J C Abadillouriel, Susan N. Coppersmith, M A Eriksson, Mark FriesenAbstract:A fundamental challenge for quantum dot spin Qubits is to extend the strength and range of Qubit interactions while suppressing their coupling to the environment, since both effects have electrical origins. Key tools include the ability to take advantage of physical resources in different regimes, and to access optimal working points, sweet spots, where dephasing is minimized. Here, we explore an important resource for singlet-triplet Qubits: a transverse sweet spot (TSS) that enables transitions between Qubit states, a strong dipolar coupling, and leading-order protection from electrical fluctuations. Of particular interest is the possibility of transitioning between the TSS and symmetric operating points while remaining continuously protected. This arrangement is ideal for coupling Qubits to a microwave cavity, because it combines tunability of the coupling with noise insensitivity. We perform simulations with $$1/f$$-type electrical noise, demonstrating that two-Qubit gates mediated by a resonator can achieve fidelities >99% under realistic conditions. Semiconductor quantum dots are controlled by external fields that are tuned in order to optimise for information storage or inter-Qubit interaction. Here the authors identify a working point for long-range interactions that can be reached with continuous protection from environmental noise.
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benchmarking gate fidelities in a si sige two Qubit device
Physical Review B, 2019Co-Authors: Xiao Xue, D E Savage, Max G. Lagally, Susan N. Coppersmith, Jonas Helsen, Stephanie Wehner, M A Eriksson, T F Watson, Daniel R Ward, L M K VandersypenAbstract:We report the first complete characterization of single-Qubit and two-Qubit gate fidelities in silicon-based spin Qubits, including cross talk and error correlations between the two Qubits. To do so, we use a combination of standard randomized benchmarking and a recently introduced method called character randomized benchmarking, which allows for more reliable estimates of the two-Qubit fidelity in this system, here giving a 92% fidelity estimate for the controlled-Z gate. Interestingly, with character randomized benchmarking, the two-Qubit gate fidelity can be obtained by studying the additional decay induced by interleaving the two-Qubit gate in a reference sequence of single-Qubit gates only. This work sets the stage for further improvements in all the relevant gate fidelities in silicon spin Qubits beyond the error threshold for fault-tolerant quantum computation.
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benchmarking gate fidelities in a si sige two Qubit device
arXiv: Quantum Physics, 2018Co-Authors: Xiao Xue, D E Savage, Max G. Lagally, Susan N. Coppersmith, Jonas Helsen, Stephanie Wehner, M A Eriksson, T F Watson, Daniel R Ward, L M K VandersypenAbstract:We report the first complete characterization of single-Qubit and two-Qubit gate fidelities in silicon-based spin Qubits, including cross-talk and error correlations between the two Qubits. To do so, we use a combination of standard randomized benchmarking and a recently introduced method called character randomized benchmarking, which allows for more reliable estimates of the two-Qubit fidelity in this system. Interestingly, with character randomized benchmarking, the two-Qubit CPhase gate fidelity can be obtained by studying the additional decay induced by interleaving the CPhase gate in a reference sequence of single-Qubit gates only. This work sets the stage for further improvements in all the relevant gate fidelities in silicon spin Qubits beyond the error threshold for fault-tolerant quantum computation.
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a programmable two Qubit quantum processor in silicon
Nature, 2018Co-Authors: T F Watson, D.R. Ward, D E Savage, Mark Friesen, Max G. Lagally, M Veldhorst, Pasquale Scarlino, S G J Philips, Erika Kawakami, Susan N. CoppersmithAbstract:Now that it is possible to achieve measurement and control fidelities for individual quantum bits (Qubits) above the threshold for fault tolerance, attention is moving towards the difficult task of scaling up the number of physical Qubits to the large numbers that are needed for fault-tolerant quantum computing. In this context, quantum-dot-based spin Qubits could have substantial advantages over other types of Qubit owing to their potential for all-electrical operation and ability to be integrated at high density onto an industrial platform. Initialization, readout and single- and two-Qubit gates have been demonstrated in various quantum-dot-based Qubit representations. However, as seen with small-scale demonstrations of quantum computers using other types of Qubit, combining these elements leads to challenges related to Qubit crosstalk, state leakage, calibration and control hardware. Here we overcome these challenges by using carefully designed control techniques to demonstrate a programmable two-Qubit quantum processor in a silicon device that can perform the Deutsch-Josza algorithm and the Grover search algorithm - canonical examples of quantum algorithms that outperform their classical analogues. We characterize the entanglement in our processor by using quantum-state tomography of Bell states, measuring state fidelities of 85-89 per cent and concurrences of 73-82 per cent. These results pave the way for larger-scale quantum computers that use spins confined to quantum dots.
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Quantum control and process tomography of a semiconductor quantum dot hybrid Qubit
Nature, 2014Co-Authors: Kim Dohun, Koh Teck Seng, J K Gamble, D.R. Ward, J. R. Prance, Shi Zhan, C B Simmons, D E Savage, Mark Friesen, Max G. Lagally, Susan N. Coppersmith, Mark A. ErikssonAbstract:The similarities between gated quantum dots and the transistors in modern microelectronics-in fabrication methods, physical structure and voltage scales for manipulation-have led to great interest in the development of quantum bits (Qubits) in semiconductor quantum dots. Although quantum dot spin Qubits have demonstrated long coherence times, their manipulation is often slower than desired for important future applications, such as factoring. Furthermore, scalability and manufacturability are enhanced when Qubits are as simple as possible. Previous work has increased the speed of spin Qubit rotations by making use of integrated micromagnets, dynamic pumping of nuclear spins or the addition of a third quantum dot. Here we demonstrate a Qubit that is a hybrid of spin and charge. It is simple, requiring neither nuclear-state preparation nor micromagnets. Unlike previous double-dot Qubits, the hybrid Qubit enables fast rotations about two axes of the Bloch sphere. We demonstrate full control on the Bloch sphere with pi-rotation times of less than 100 picoseconds in two orthogonal directions, which is more than an order of magnitude faster than any other double-dot Qubit. The speed arises from the Qubit's charge-like characteristics, and its spin-like features result in resistance to decoherence over a wide range of gate voltages. We achieve full process tomography in our electrically controlled semiconductor quantum dot Qubit, extracting high fidelities of 85 per cent for X rotations (transitions between Qubit states) and 94 per cent for Z rotations (phase accumulation between Qubit states).
Chui-ping Yang - One of the best experts on this subject based on the ideXlab platform.
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Multiplex-controlled phase gate with Qubits distributed in a multicavity system
Physical Review A, 2018Co-Authors: Biaoliang Ye, Zhen-fei Zheng, Chui-ping YangAbstract:We present a way to realize a multiplex-controlled phase gate of n-1 control Qubits simultaneously controlling one target Qubit, with n Qubits distributed in n different cavities. This multiQubit gate is implemented by using n qutrits (three-level natural or artificial atoms) placed in n different cavities, which are coupled to an auxiliary qutrit. Here, the two logic states of a Qubit are represented by the two lowest levels of a qutrit placed in a cavity. We show that this n-Qubit controlled phase gate can be realized using only 2n+2 basic operations, i.e., the number of required basic operations only increases linearly with the number n of Qubits. Since each basic operation employs the qutrit-cavity or qutrit-pulse resonant interaction, the gate can be fast implemented when the number of Qubits is not large. Numerical simulations show that a three-Qubit controlled phase gate, which is executed on three Qubits distributed in three different cavities, can be high-fidelity implemented by using a circuit QED system. This proposal is quite general and can be applied to a wide range of physical systems, with atoms, NV centers, quantum dots, or various superconducting qutrits distributed in different cavities. Finally, this method can be applied to implement a multiQubit controlled phase gate with atoms using a cavity. A detailed discussion on implementing a three-Qubit controlled phase gate with atoms and one cavity is presented.
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Multi-target-Qubit unconventional geometric phase gate in a multi-cavity system
Scientific Reports, 2016Co-Authors: Qi-ping Su, Shao-jie Xiong, Chui-ping YangAbstract:: Cavity-based large scale quantum information processing (QIP) may involve multiple cavities and require performing various quantum logic operations on Qubits distributed in different cavities. Geometric-phase-based quantum computing has drawn much attention recently, which offers advantages against inaccuracies and local fluctuations. In addition, multiQubit gates are particularly appealing and play important roles in QIP. We here present a simple and efficient scheme for realizing a multi-target-Qubit unconventional geometric phase gate in a multi-cavity system. This multiQubit phase gate has a common control Qubit but different target Qubits distributed in different cavities, which can be achieved using a single-step operation. The gate operation time is independent of the number of Qubits and only two levels for each Qubit are needed. This multiQubit gate is generic, e.g., by performing single-Qubit operations, it can be converted into two types of significant multi-target-Qubit phase gates useful in QIP. The proposal is quite general, which can be used to accomplish the same task for a general type of Qubits such as atoms, NV centers, quantum dots, and superconducting Qubits.
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Phase gate of one Qubit simultaneously controlling n Qubits in a cavity
Physical Review A, 2010Co-Authors: Chui-ping Yang, Franco NoriAbstract:We propose how to realize a three-step controlled-phase gate of one Qubit simultaneously controlling n Qubits in a cavity or coupled to a resonator. The n two-Qubit controlled-phase gates, forming this multiQubit phase gate, can be performed simultaneously. The operation time of this phase gate is independent of the number n of Qubits. This phase gate controlling at once n Qubits is insensitive to the initial state of the cavity mode and can be used to produce an analogous cnot gate simultaneously acting on n Qubits. We present two alternative approaches to implement this gate. One approach is based on tuning the Qubit frequency while in the other method the resonator frequency is tuned. Using superconducting Qubits coupled to a resonator as an example, we show how to implement the proposed gate with one superconducting Qubit simultaneously controlling n Qubits selected from N Qubits coupled to a resonator (1
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phase gate of one Qubit simultaneously controlling n Qubits in a cavity
arXiv: Quantum Physics, 2009Co-Authors: Chui-ping Yang, Franco NoriAbstract:We propose how to realize a three-step controlled-phase gate of one Qubit simultaneously controlling $n$ Qubits in a cavity or coupled to a resonator. The $n$ two-Qubit controlled-phase gates, forming this multiQubit phase gate, can be performed simultaneously. The operation time of this phase gate is independent of the number $n$ of Qubits. This phase gate controlling at once $n$ Qubits is insensitive to the initial state of the cavity mode and can be used to produce an analogous CNOT gate simultaneously acting on $n$ Qubits. We present two alternative approaches to implement this gate. One approach is based on tuning the Qubit frequency while the other method tunes the resonator frequency. Using superconducting Qubits coupled to a resonator as an example, we show how to implement the proposed gate with one superconducting Qubit simultaneously controlling $n$ Qubits selected from $N$ Qubits coupled to a resonator ($1
D E Savage - One of the best experts on this subject based on the ideXlab platform.
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benchmarking gate fidelities in a si sige two Qubit device
Physical Review B, 2019Co-Authors: Xiao Xue, D E Savage, Max G. Lagally, Susan N. Coppersmith, Jonas Helsen, Stephanie Wehner, M A Eriksson, T F Watson, Daniel R Ward, L M K VandersypenAbstract:We report the first complete characterization of single-Qubit and two-Qubit gate fidelities in silicon-based spin Qubits, including cross talk and error correlations between the two Qubits. To do so, we use a combination of standard randomized benchmarking and a recently introduced method called character randomized benchmarking, which allows for more reliable estimates of the two-Qubit fidelity in this system, here giving a 92% fidelity estimate for the controlled-Z gate. Interestingly, with character randomized benchmarking, the two-Qubit gate fidelity can be obtained by studying the additional decay induced by interleaving the two-Qubit gate in a reference sequence of single-Qubit gates only. This work sets the stage for further improvements in all the relevant gate fidelities in silicon spin Qubits beyond the error threshold for fault-tolerant quantum computation.
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benchmarking gate fidelities in a si sige two Qubit device
arXiv: Quantum Physics, 2018Co-Authors: Xiao Xue, D E Savage, Max G. Lagally, Susan N. Coppersmith, Jonas Helsen, Stephanie Wehner, M A Eriksson, T F Watson, Daniel R Ward, L M K VandersypenAbstract:We report the first complete characterization of single-Qubit and two-Qubit gate fidelities in silicon-based spin Qubits, including cross-talk and error correlations between the two Qubits. To do so, we use a combination of standard randomized benchmarking and a recently introduced method called character randomized benchmarking, which allows for more reliable estimates of the two-Qubit fidelity in this system. Interestingly, with character randomized benchmarking, the two-Qubit CPhase gate fidelity can be obtained by studying the additional decay induced by interleaving the CPhase gate in a reference sequence of single-Qubit gates only. This work sets the stage for further improvements in all the relevant gate fidelities in silicon spin Qubits beyond the error threshold for fault-tolerant quantum computation.
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a programmable two Qubit quantum processor in silicon
Nature, 2018Co-Authors: T F Watson, D.R. Ward, D E Savage, Mark Friesen, Max G. Lagally, M Veldhorst, Pasquale Scarlino, S G J Philips, Erika Kawakami, Susan N. CoppersmithAbstract:Now that it is possible to achieve measurement and control fidelities for individual quantum bits (Qubits) above the threshold for fault tolerance, attention is moving towards the difficult task of scaling up the number of physical Qubits to the large numbers that are needed for fault-tolerant quantum computing. In this context, quantum-dot-based spin Qubits could have substantial advantages over other types of Qubit owing to their potential for all-electrical operation and ability to be integrated at high density onto an industrial platform. Initialization, readout and single- and two-Qubit gates have been demonstrated in various quantum-dot-based Qubit representations. However, as seen with small-scale demonstrations of quantum computers using other types of Qubit, combining these elements leads to challenges related to Qubit crosstalk, state leakage, calibration and control hardware. Here we overcome these challenges by using carefully designed control techniques to demonstrate a programmable two-Qubit quantum processor in a silicon device that can perform the Deutsch-Josza algorithm and the Grover search algorithm - canonical examples of quantum algorithms that outperform their classical analogues. We characterize the entanglement in our processor by using quantum-state tomography of Bell states, measuring state fidelities of 85-89 per cent and concurrences of 73-82 per cent. These results pave the way for larger-scale quantum computers that use spins confined to quantum dots.
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Quantum control and process tomography of a semiconductor quantum dot hybrid Qubit
Nature, 2014Co-Authors: Kim Dohun, Koh Teck Seng, J K Gamble, D.R. Ward, J. R. Prance, Shi Zhan, C B Simmons, D E Savage, Mark Friesen, Max G. Lagally, Susan N. Coppersmith, Mark A. ErikssonAbstract:The similarities between gated quantum dots and the transistors in modern microelectronics-in fabrication methods, physical structure and voltage scales for manipulation-have led to great interest in the development of quantum bits (Qubits) in semiconductor quantum dots. Although quantum dot spin Qubits have demonstrated long coherence times, their manipulation is often slower than desired for important future applications, such as factoring. Furthermore, scalability and manufacturability are enhanced when Qubits are as simple as possible. Previous work has increased the speed of spin Qubit rotations by making use of integrated micromagnets, dynamic pumping of nuclear spins or the addition of a third quantum dot. Here we demonstrate a Qubit that is a hybrid of spin and charge. It is simple, requiring neither nuclear-state preparation nor micromagnets. Unlike previous double-dot Qubits, the hybrid Qubit enables fast rotations about two axes of the Bloch sphere. We demonstrate full control on the Bloch sphere with pi-rotation times of less than 100 picoseconds in two orthogonal directions, which is more than an order of magnitude faster than any other double-dot Qubit. The speed arises from the Qubit's charge-like characteristics, and its spin-like features result in resistance to decoherence over a wide range of gate voltages. We achieve full process tomography in our electrically controlled semiconductor quantum dot Qubit, extracting high fidelities of 85 per cent for X rotations (transitions between Qubit states) and 94 per cent for Z rotations (phase accumulation between Qubit states).
Max G. Lagally - One of the best experts on this subject based on the ideXlab platform.
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benchmarking gate fidelities in a si sige two Qubit device
Physical Review B, 2019Co-Authors: Xiao Xue, D E Savage, Max G. Lagally, Susan N. Coppersmith, Jonas Helsen, Stephanie Wehner, M A Eriksson, T F Watson, Daniel R Ward, L M K VandersypenAbstract:We report the first complete characterization of single-Qubit and two-Qubit gate fidelities in silicon-based spin Qubits, including cross talk and error correlations between the two Qubits. To do so, we use a combination of standard randomized benchmarking and a recently introduced method called character randomized benchmarking, which allows for more reliable estimates of the two-Qubit fidelity in this system, here giving a 92% fidelity estimate for the controlled-Z gate. Interestingly, with character randomized benchmarking, the two-Qubit gate fidelity can be obtained by studying the additional decay induced by interleaving the two-Qubit gate in a reference sequence of single-Qubit gates only. This work sets the stage for further improvements in all the relevant gate fidelities in silicon spin Qubits beyond the error threshold for fault-tolerant quantum computation.
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benchmarking gate fidelities in a si sige two Qubit device
arXiv: Quantum Physics, 2018Co-Authors: Xiao Xue, D E Savage, Max G. Lagally, Susan N. Coppersmith, Jonas Helsen, Stephanie Wehner, M A Eriksson, T F Watson, Daniel R Ward, L M K VandersypenAbstract:We report the first complete characterization of single-Qubit and two-Qubit gate fidelities in silicon-based spin Qubits, including cross-talk and error correlations between the two Qubits. To do so, we use a combination of standard randomized benchmarking and a recently introduced method called character randomized benchmarking, which allows for more reliable estimates of the two-Qubit fidelity in this system. Interestingly, with character randomized benchmarking, the two-Qubit CPhase gate fidelity can be obtained by studying the additional decay induced by interleaving the CPhase gate in a reference sequence of single-Qubit gates only. This work sets the stage for further improvements in all the relevant gate fidelities in silicon spin Qubits beyond the error threshold for fault-tolerant quantum computation.
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a programmable two Qubit quantum processor in silicon
Nature, 2018Co-Authors: T F Watson, D.R. Ward, D E Savage, Mark Friesen, Max G. Lagally, M Veldhorst, Pasquale Scarlino, S G J Philips, Erika Kawakami, Susan N. CoppersmithAbstract:Now that it is possible to achieve measurement and control fidelities for individual quantum bits (Qubits) above the threshold for fault tolerance, attention is moving towards the difficult task of scaling up the number of physical Qubits to the large numbers that are needed for fault-tolerant quantum computing. In this context, quantum-dot-based spin Qubits could have substantial advantages over other types of Qubit owing to their potential for all-electrical operation and ability to be integrated at high density onto an industrial platform. Initialization, readout and single- and two-Qubit gates have been demonstrated in various quantum-dot-based Qubit representations. However, as seen with small-scale demonstrations of quantum computers using other types of Qubit, combining these elements leads to challenges related to Qubit crosstalk, state leakage, calibration and control hardware. Here we overcome these challenges by using carefully designed control techniques to demonstrate a programmable two-Qubit quantum processor in a silicon device that can perform the Deutsch-Josza algorithm and the Grover search algorithm - canonical examples of quantum algorithms that outperform their classical analogues. We characterize the entanglement in our processor by using quantum-state tomography of Bell states, measuring state fidelities of 85-89 per cent and concurrences of 73-82 per cent. These results pave the way for larger-scale quantum computers that use spins confined to quantum dots.
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Quantum control and process tomography of a semiconductor quantum dot hybrid Qubit
Nature, 2014Co-Authors: Kim Dohun, Koh Teck Seng, J K Gamble, D.R. Ward, J. R. Prance, Shi Zhan, C B Simmons, D E Savage, Mark Friesen, Max G. Lagally, Susan N. Coppersmith, Mark A. ErikssonAbstract:The similarities between gated quantum dots and the transistors in modern microelectronics-in fabrication methods, physical structure and voltage scales for manipulation-have led to great interest in the development of quantum bits (Qubits) in semiconductor quantum dots. Although quantum dot spin Qubits have demonstrated long coherence times, their manipulation is often slower than desired for important future applications, such as factoring. Furthermore, scalability and manufacturability are enhanced when Qubits are as simple as possible. Previous work has increased the speed of spin Qubit rotations by making use of integrated micromagnets, dynamic pumping of nuclear spins or the addition of a third quantum dot. Here we demonstrate a Qubit that is a hybrid of spin and charge. It is simple, requiring neither nuclear-state preparation nor micromagnets. Unlike previous double-dot Qubits, the hybrid Qubit enables fast rotations about two axes of the Bloch sphere. We demonstrate full control on the Bloch sphere with pi-rotation times of less than 100 picoseconds in two orthogonal directions, which is more than an order of magnitude faster than any other double-dot Qubit. The speed arises from the Qubit's charge-like characteristics, and its spin-like features result in resistance to decoherence over a wide range of gate voltages. We achieve full process tomography in our electrically controlled semiconductor quantum dot Qubit, extracting high fidelities of 85 per cent for X rotations (transitions between Qubit states) and 94 per cent for Z rotations (phase accumulation between Qubit states).
Alexandre Blais - One of the best experts on this subject based on the ideXlab platform.
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coherent spin photon coupling using a resonant exchange Qubit
Nature, 2018Co-Authors: Andreas Landig, Andreas Wallraff, Alexandre Blais, Jonne V Koski, Pasquale Scarlino, Udson C Mendes, Christian Reichl, Werner Wegscheider, K EnsslinAbstract:Electron spins hold great promise for quantum computation because of their long coherence times. Long-distance coherent coupling of spins is a crucial step towards quantum information processing with spin Qubits. One approach to realizing interactions between distant spin Qubits is to use photons as carriers of quantum information. Here we demonstrate strong coupling between single microwave photons in a niobium titanium nitride high-impedance resonator and a three-electron spin Qubit (also known as a resonant exchange Qubit) in a gallium arsenide device consisting of three quantum dots. We observe the vacuum Rabi mode splitting of the resonance of the resonator, which is a signature of strong coupling; specifically, we observe a coherent coupling strength of about 31 megahertz and a Qubit decoherence rate of about 20 megahertz. We can tune the decoherence electrostatically to obtain a minimal decoherence rate of around 10 megahertz for a coupling strength of around 23 megahertz. We directly measure the dependence of the Qubit–photon coupling strength on the tunable electric dipole moment of the Qubit using the ‘AC Stark’ effect. Our demonstration of strong Qubit–photon coupling for a three-electron spin Qubit is an important step towards coherent long-distance coupling of spin Qubits. Coherent coupling between a three-electron spin Qubit and single photons in a microwave resonator is demonstrated, which, unlike previous demonstrations, does not require ferromagnetic components near the Qubit.
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Quantum Codes for Simplifying Design and Suppressing Decoherence in Superconducting Phase-Qubits
Quantum Information Processing, 2002Co-Authors: Daniel A. Lidar, Alexandre BlaisAbstract:We introduce simple Qubit-encodings and logic gates which eliminate the need for certain difficult single-Qubit operations in superconducting phase-Qubits, while preserving universality. The simplest encoding uses two physical Qubits per logical Qubit. Two architectures for its implementation are proposed: one employing N physical Qubits out of which N /2 are ancillas fixed in the |1 state, the other employing N /2+1 physical Qubits, one of which is a bus Qubit connected to all others. Details of a minimal set of universal encoded logic operations are given, together with recoupling schemes, that require nanosecond pulses. A generalization to codes with higher ratio of number of logical Qubits per physical Qubits is presented. Compatible decoherence and noise suppression strategies are also discussed. PACS: 03.67.Lx; 85.25.Hv; 03.67.-a; 89.70.+c
