Roles of frames and ports - Amazon Braket

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Roles of frames and ports

This section describes the predefined frames and ports available for each device. We will also briefly discuss the mechanisms involved when pulses are played on certain frames.

Rigetti

Frames

Rigetti devices support predefined frames that have their frequency and phase calibrated to be on resonance with the associated qubit. The naming convention is q{i}[_q{j}]_{role}_frame where {i} refers to the first qubit number, {j} refers to the second qubit number in case the frame serves to activate a two-qubit interaction, and {role} refers to the role of the frame. The roles are as follows:

  • rf is the frame to drive the 0-1 transition of the qubit. Pulses are transmitted as microwave transient signals of frequency and phase previously provided through the set and shift functions. The time-dependent amplitude of the signal is given by the waveform played on the frame. The frame plugs a single-qubit, off-diagonal interaction. For more information, see Krantz et al. and Rahamim et al..

  • rf_f12 is similar to rf and its parameters target the 1-2 transition.

  • ro_rx is used to achieve dispersive readout of the qubit through a coupled coplanar waveguide. The frequency, phase, and full set of parameters for the readout waveform are precalibrated. It is currently used via the capture_v0, which does not require any argument besides the frame identifier.

  • ro_tx is for transmitting signals from the resonator. It is currently unused.

  • cz is a frame calibrated to enable the two-qubit cz gate. As with all the frames associated with an ff port, it turns on an entangling interaction through the flux line by modulating the tunable qubit of the pair on resonance with its neighbor. For more information about the entangling mechanism, see Reagor et al., Caldwell et al., and Didier et al..

  • cphase is a frame calibrated to enable the two-qubit cphaseshift gate and is linked to an ff port. For more information about the entangling mechanism, see the description for the cz frame.

  • xy is a frame calibrated to enable the two-qubit XY(θ) gates and is linked to an ff port. For more information about the entangling mechanism and how to achieve XY gates, see the description for the cz frame and Abrams et al..

As frames based on the ff port shift the frequency of the tunable qubit, all the other driving frames related to the qubit will be dephased by an amount that is related to the amplitude and the duration of the frequency shift. Consequently, you must compensate for this effect by adding a corresponding phase shift to the frames of the neighboring qubits.

Ports

The Rigetti devices provide a list of ports that you can inspect through the device capabilities. Port names follow the convention q{i}_{type} where {i} refers to the qubit number and {type} refers to the type of the port. Note that not all of the qubits have a complete set of ports. The types of ports are as follows:

  • rf represents the main interface to drive the single-qubit transition. It is associated with the rf and rf_f12 frames. It is capacitively coupled to the qubit, allowing microwave driving in the gigahertz range.

  • ro_tx serves to transmit signals to the readout resonator capacitively coupled to the qubit. Readout signal delivery is multiplexed eight-fold by octagon.

  • ro_rx serves to receive signals from the readout resonator coupled to the qubit.

  • ff represents the fast-flux line inductively coupled to the qubit. We can use this to tune the frequency of the transmon. Only qubits designed to be highly tunable have an ff port. This port serves to activate qubit-qubit interaction as there is a static capacitive coupling between each pair of neighboring transmons.

For more information about the architecture, see Valery et al..

OQC

Frames

OQC devices support predefined frames that have their frequency and phase calibrated to be on resonance with the associated qubit. The naming convention for these frames is as follows:

  • driving frame: q{i}[_q{j}]_{role} where {i} refers to the first qubit number, {j} refers to the second qubit number in case the frame serves to activate a two-qubit interaction, and {role} refers to the role of the frame as described below.

  • qubit readout frame: r{i}_{role} where {i} refers to the qubit number and {role} refers to the role of the frame as described below.

We recommend using each frame for its designed role as follows:

  • drive is used as the main frame to drive the 0-1 transition of the qubit. Pulses are transmitted as microwave transient signals of frequency and phase previously provided through the set and shift functions. The time-dependent amplitude of the signal is given by the waveform played on the frame. The frame plugs a single-qubit, off-diagonal interaction. For more information, see Krantz et al. and Rahamim et al..

  • second_state is equivalent to the drive frame but its frequency is tuned on resonance with the 1-2 transition.

  • measure is for readout. The frequency, phase, and full set of parameters for the readout waveform are precalibrated. It is currently used through the capture_v0, which does not require any argument besides the frame identifier.

  • acquire is for capturing signals from the resonator. It is currently unused.

  • cross_resonance activates the cross resonance interaction between the qubits i and j by driving the control qubit i at the transition frequency of the target qubit j. Consequently, the frame frequency is set using the frequency of the target qubit. The interaction occurs with a rate proportional to the amplitude of this cross-resonant drive. Different types of crosstalks induces unwanted effects which requires corrections. See Patterson et al. for more information about the cross-resonance interaction with coaxially-shaped transmon qubits (‘coaxmons’).

  • cross_resonance_cancellation helps you add corrections to suppress deleterious effects induced by crosstalks when the cross-resonance interaction is activated. The initial frame frequency is set to the transition frequency of the control qubit i. For more information about the cancellation method, see Patterson et al..

Ports

The OQC devices provide a list of ports that you can inspect through the device capabilities. The previously described frames are associated with ports that are identified by their id channel_{N} where {N} is an integer. Ports are the interface to control lines (direction tx) and readout resonators (direction rx) connected to coaxmons. Each qubit is associated to one control line and one readout resonator. The transmission port is the interface for single-qubit and two-qubit manipulation. The reception port serves for qubit readout.