本文為英文版的機器翻譯版本，如內容有任何歧義或不一致之處，概以英文版為準。

# 從 Amazon Braket SDK 追蹤量子任務
<a name="braket-monitor-tasks-sdk"></a>

命令`device.run(…​)`會定義具有唯一量子任務 ID 的量子任務。您可以使用 查詢和追蹤狀態`task.state()`，如下列範例所示。

 **注意**： `task = device.run()` 是一種非同步操作，這表示您可以在系統在背景處理量子任務時繼續工作。

 **擷取結果** 

當您呼叫 時`task.result()`，開發套件會開始輪詢 Amazon Braket，以查看量子任務是否完成。SDK 會使用您在 中定義的輪詢參數`.run()`。量子任務完成後，開發套件會從 S3 儲存貯體擷取結果，並將其傳回為`QuantumTaskResult`物件。

```
# create a circuit, specify the device and run the circuit
circ = Circuit().rx(0, 0.15).ry(1, 0.2).cnot(0,2)
device = AwsDevice("arn:aws:braket:::device/quantum-simulator/amazon/sv1")
task = device.run(circ, s3_location, shots=1000)

# get ID and status of submitted task
task_id = task.id
status = task.state()
print('ID of task:', task_id)
print('Status of task:', status)
# wait for job to complete
while status != 'COMPLETED':
    status = task.state()
    print('Status:', status)
```

```
ID of task:
arn:aws:braket:us-west-2:123412341234:quantum-task/b68ae94b-1547-4d1d-aa92-1500b82c300d
Status of task: QUEUED
Status: QUEUED
Status: QUEUED
Status: QUEUED
Status: QUEUED
Status: QUEUED
Status: QUEUED
Status: QUEUED
Status: RUNNING
Status: RUNNING
Status: COMPLETED
```

 **取消量子任務** 

若要取消量子任務，請呼叫 `cancel()`方法，如下列範例所示。

```
# cancel quantum task
task.cancel()
status = task.state()
print('Status of task:', status)
```

```
Status of task: CANCELLING
```

 **檢查中繼資料** 

您可以檢查已完成量子任務的中繼資料，如下列範例所示。

```
# get the metadata of the quantum task
metadata = task.metadata()
# example of metadata
shots = metadata['shots']
date = metadata['ResponseMetadata']['HTTPHeaders']['date']
# print example metadata
print("{} shots taken on {}.".format(shots, date))

# print name of the s3 bucket where the result is saved
results_bucket = metadata['outputS3Bucket']
print('Bucket where results are stored:', results_bucket)
# print the s3 object key (folder name)
results_object_key = metadata['outputS3Directory']
print('S3 object key:', results_object_key)

# the entire look-up string of the saved result data
look_up = 's3://'+results_bucket+'/'+results_object_key
print('S3 URI:', look_up)
```

```
1000 shots taken on Wed, 05 Aug 2020 14:44:22 GMT.
Bucket where results are stored: amazon-braket-123412341234
S3 object key: simulation-output/b68ae94b-1547-4d1d-aa92-1500b82c300d
S3 URI: s3://amazon-braket-123412341234/simulation-output/b68ae94b-1547-4d1d-aa92-1500b82c300d
```

 **擷取量子任務或結果** 

如果您的核心在您提交量子任務後死亡，或者您關閉筆記本或電腦，您可以使用其唯一的 ARN （量子任務 ID) 重建`task`物件。然後，您可以呼叫 從儲存該儲存貯體的 S3 儲存貯體`task.result()`取得結果。

```
from braket.aws import AwsSession, AwsQuantumTask

# restore task with unique arn
task_load = AwsQuantumTask(arn=task_id)
# retrieve the result of the task
result = task_load.result()
```