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Add registry sweep documentation to cirq_google #6291

Merged
merged 8 commits into from
Sep 20, 2023
69 changes: 35 additions & 34 deletions docs/google/devices.md
Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@ of total circuit run-time. Circuits that exceed this limit will return a

### Moment structure

The hardware will attempt to run your circuit as it exists in cirq to the
The hardware will attempt to run your circuit as it exists in Cirq to the
extent possible. The device will respect the moment structure of your circuit
and will execute successive moments in a serial fashion.

Expand Down Expand Up @@ -65,11 +65,40 @@ cirq.Circuit(

The duration of a moment is the time of its longest gate. For example,
if a moment has gates of duration 12ns, 25ns, and 32ns, the entire moment
will take 32ns. Qubits executing the shorter gtes will idle during the rest
will take 32ns. Qubits executing the shorter gates will idle during the rest
of the time. To minimize the duration of the circuit, it is best to align
gates of the same duration together when possible. See the
[best practices](./best_practices.ipynb) for more details.

## Device Parameter Sweeps

Certain device parameters can be changed for the duration of
a circuit in order to support hardware parameter sweeps. For instance,
frequencies, amplitudes, and various other parameters can be modified
in order to find optimal values or explore the parameter space.

These parameter names are generally not public, so you will need to
work with a Google sponsor or resident in order to access the proper
key names. These parameters are specified as lists of strings representing
a path from the device config's folder (or the "sample folder").

These keys can be swept like any other symbol using the
`cirq_google.study.DeviceParameter` variable. For instance, the
following code will sweep qubit (4,8)'s pi amplitude from 0.0 to 1.0
in 0.02 increments.


```
descriptor = cirq_google.study.DeviceParameter( ["q4_8", "piAmp"])
sweep = cirq.Linspace("q4_8.piAmp", 0, 1, 51, metadata=descriptor)
```

Any `DeviceParameter` keys that are set to a single value using a `cirq.Points`
object will change that value for all circuits run.

If units are required, they should be specified as a string (such as 'MHz')
using the `units` argument of the `DeviceParameter`.

## Gates supported

The following lists the gates supported by Google devices.
Expand Down Expand Up @@ -188,7 +217,7 @@ $$
This gate has a duration of 32ns and can be used in
`cirq_google.SQRT_ISWAP_GATESET` or in the `cirq_google.FSIM_GATESET`.

This gate is implemented by using an entangling gate surrounding by
This gate is implemented by using an entangling gate surrounded by
Z gates. The preceding Z gates are physical Z gates and will absorb
any phases that have accumulated through the use of Virtual Z gates.
Following the entangler are virtual Z gates to match phases back. All
Expand Down Expand Up @@ -238,7 +267,8 @@ expressions, but only a subset of Sympy expression types are supported:
`sympy.Symbol`, `sympy.Add`, `sympy.Mul`, and `sympy.Pow`.

## Specific Device Layouts
The following devices are provided as part of cirq and can help you get your

The following devices are provided as part of Cirq and can help you get your
circuit ready for running on hardware by verifying that you are using
appropriate qubits.

Expand Down Expand Up @@ -272,7 +302,7 @@ It can be accessed using `cirq.GridQubit(row, col)` using grid coordinates speci
9 ----I-----
```

It can be accessing by using `cirq_google.Sycamore`. This device has two possible
It can be accessed by using `cirq_google.Sycamore`. This device has two possible
two-qubits gates that can be used.

* Square root of ISWAP. The gate `cirq.ISWAP ** 0.5` or `cirq.ISWAP ** -0.5` can be
Expand Down Expand Up @@ -304,32 +334,3 @@ with and presents less hardware-related complications than using the full Sycamo

This grid can be accessed using `cirq_google.Sycamore23` and uses the same gate sets and
compilation as the Sycamore device.


### Bristlecone

The Bristlecone processor is a 72 qubit device
[announced by Google in 2018](https://ai.googleblog.com/2018/03/a-preview-of-bristlecone-googles-new.html).

The device is arrayed on a grid in a diamond pattern like this.

```
11
012345678901
0 -----AB-----
1 ----ABCD----
2 ---ABCDEF---
3 --ABCDEFGH--
4 -ABCDEFGHIJ-
5 ABCDEFGHIJKL
6 -CDEFGHIJKL-
7 --EFGHIJKL--
8 ---GHIJKL---
9 ----IJKL----
10-----KL-----
```

It can be accessing by using `cirq_google.Bristlecone`. Circuits can be compiled to it by using
`cirq_google.optimized_for_xmon` or by using `cirq_google.optimized_for_sycamore` with
optimizer_type `xmon`.

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